If a classic pickup has any trace of its original suspension left in place, it's going to ride and handle a lot better if it has a load in the bed. This is because all trucks are factory engineered to function under the assumption that they are going to spend most of their life working with extra weight over the rear axle. The extra weight brings the front-to-rear weight distribution closer to the ideal 50/50 balance and nothing but good things begin to happen. Under acceleration the truck has better traction, and when it's time to jump on the binders, provided it's not over loaded, the truck is going to stop better.
When the subject changes to customized classic trucks where the suspension has been upgraded with a modern system including lighter spring rates the ride will be "softer", but the truck will remain nose heavy. In general, the solution is to redistribute the weight, and moving the gas tank as far rearward as possible is one of the best solutions. What this means in almost every case is a custom-made rear gas tank will have to be fabricated or purchased, and then installed. For owners of '67-'72 Chevrolet and GMC pickups there is an option that costs less and as part of the deal, throws in a factory original appearance. The gas tank we're talking about is a reproduction of the 21-gallon tank General Motors engineered as standard equipment for the Blazer. Since it is patterned exactly after the original, any of the goodies that might go bad in the future such as the gas gauge sending unit, can be sourced from any auto parts store. Naturally since the tank kit we installed was originally sourced from LMC Truck, of Lenexa, Kansas, that would be the first place to look for replacement parts.
The subject vehicle in this instance is the '68 GMC longbed known as "Agent Orange," which has appeared in previous issues. At some point, the '68 will undergo shortbed surgery and be turned into a cruiser. In the meantime, it's still being used as a hard working truck. In town hauling a heavy load or pulling a trailer, the '68 is lucky to get more than 10 miles per gallon. Pushing it with the stock in cab 16-gallon tank, it's lucky to cover 150 miles.
As a rule when it comes to in cab gas tanks, I like to relocate to where I believe is a safer location, but this time around I'm going to take my chances and build what's called a "tanker." I left the stock tank in place and installed LMC Truck's 21-gallon Blazer tank as a "saddle tank" giving the old girl a total of 35 gallons. As an interesting trivial fact, the Chevrolet Blazers built specifically for military use came equipped with a 27-gallon gas tank built to mil-specs. A few years ago a batch of new, old-stock military spec 27-gallon tanks showed up as Army surplus, but I doubt there's any to be found on the market these days.
Direct from LMC Truck (part...
Direct from LMC Truck (part #32-5924), the rear mount gas tank comes as a kit that includes mounting straps, hardware, and a fuel gauge sending unit. This kit fits '67-'72 as well as '63-'66 C10 applications.
Try to remember the last time...
Try to remember the last time you needed a spare tire versus better fuel capacity; the only downside, and it's minor, is the mounting location for the spare tire is where LMC Truck's 21-gallon Blazer tank will find its new home. Removing the spare tire cradle was a simple matter of unbolting and setting it aside.
Next, in order to gain ground...
Next, in order to gain ground and mounting clearance for the 21-gallon tank, the top part of the spare tire cradle was cut out and removed.
Instead of grinding the rivets...
Instead of grinding the rivets off, we used a reciprocating saw to cut the stamped channel from the frame. Notice it was cut flush with the framerail.
The next step was to lift...
The next step was to lift the Blazer tank into place with the filler neck located on the driver side and check for further obstructions preventing the tank from tucking up as close as possible to the framerails.
One of the bed's cross sills...
One of the bed's cross sills needed to be trimmed for the tank to fit. There's several ways to cut steel, one is to use a pneumatic die grinder with a 4-inch cutoff disc - we used a plasma cutter, and that's the hot ticket!
This shows how much metal...
This shows how much metal was removed from the cross sill. A die grinder with a 4-inch disc was used to clean up the slag.
There are four locating tabs...
There are four locating tabs on the Blazer tank that protrude from the holes that are going to be used as bolt holes for the mounting straps. In order to let the tank sit as flush as possible, the four tabs must be cut off. Then we used a die grinder with a Harbor Freight router bit to hog the holes out to size.
Here's the mounting hole location...
Here's the mounting hole location once the modification is complete. Notice they are no larger than the original hole.
In addition to providing superior...
In addition to providing superior soundproofing, Dynamat can be used to ensure against squeaks and rattles emanating from the tank.
The sending unit must be installed...
The sending unit must be installed before mounting the Blazer tank into place. Make sure the retaining ring is driven completely into place.
The stainless steel mounting...
The stainless steel mounting strap shown at the bottom is how they arrive from LMC Truck. The straps are quite malleable and were literally easy to shape by hand as required for our intentions (top).
Using the tank as a guide,...
Using the tank as a guide, we drilled the four 3/8-inch mounting holes in the framerail.
Here's the tank in place and...
Here's the tank in place and installed on the mounting straps.
Using a hydraulic motorcycle...
Using a hydraulic motorcycle lift made it a one-man job to install the bumper.
The mounting bolts were left...
The mounting bolts were left snug but loose enough to shift the bumper around to align it into place.
A pneumatic impact wrench...
A pneumatic impact wrench makes short work out of final tightening.
With the bed wood missing,...
With the bed wood missing, one can see where the sending unit ends up. It's important to note the fuel lines, and wiring must be completely attached before the tank is lifted into place for the last time.
With its thick coating of...
With its thick coating of silver paint, LMC Truck's 21-gallon gas tank is nice to look at, but we felt in the interest of safety, it might be a good idea to install a heavy-duty rear bumper to protect it. Step one to installing LMC Truck's chrome rear-step bumper was to bolt the mounting brackets onto the existing factory boltholes.
Before lifting the rear bumper...
Before lifting the rear bumper into place, measurements were taken to ensure everything would line up.