Everybody knows it's possible to convert your vintage 1953-56 Ford F-100 small window pickup cab to a big window pickup cab with relative ease. All you have to do is buy an aftermarket kit and either install it yourself, or have it installed by a capable body shop. However, when it comes to doing the same thing to a classic, Second Series '55-59 Chevrolet or GMC, it's a little more complicated, but not in the least bit impossible.

"The basic principle is pretty much the same with both the Ford F-100 and the mid-'50s GM light duty trucks," commented Cimtex Rods' Darrell Cimbanin. "Both of these cabs feature dual wall construction and are easy to work on. The only difference is that no one out there in the automotive aftermarket offers a big window conversion kit for early Chevrolet or GMC trucks."

So what's a mother to do? The good news is that there are plenty of '55-59 Chevrolet/GMC big window cabs sitting out there in junkyards (especially in the West) that, sadly, may only be good for one thing, their big back windows.

"These '55-59 Chevrolet/GMC cabs usually suffer from seriously rusted floorpans and body rot on the lower quarter panels. The good news is that when it comes to the rear window area, early Chevrolet/GMC trucks seem to exhibit little or no rust damage, and you can usually buy the rear window clip from these old cabs for approximately $250!"

However, Cimbanin cautions would-be big back window conversion specialists that in order to do the job right, it's necessary to make sure you also receive the inner wall substructure as part of your classic Chevrolet/GMC big back window clip.

"You need this piece to strengthen the cab's outer wall," said Darrell. "On small window cabs, the surrounding sheetmetal area provides the cab's rear wall with all the necessary strength it needs. However, with a big back window model, that strength is gone, so it was necessary for the factory to provide an inner wall to shore up and strengthen the back of the cab."

Installing one of these big back windows is pretty straightforward. First, you have to remove the pickup bed in order to gain full access to the back of the cab. Removing the gas tank comes next, as you're going to be working in a "hot" area. And finally, removing the small back window glass and the factory bench seat pretty much clears the way for reconstructive surgery.