When the time came to really start thinking about dropping the LS/T-56 combo into my 1968, the only thing that really concerned me was the clearance issue that might arise due to the low-hump pan on the cab's floor. I didn't want to pull the motor in and out while I whittled away at the stock pan, grafting sheetmetal where it needed clearance and since all the carpet kits are premolded to either the low- or high-hump floors, I didn't want to deviate too much from the stock shape of the trans tunnel either so as to avoid any unsightly bulges or sags in the carpet. I knew that the high-hump trans pans were installed on a number of different spec trucks back in the day (4x4, big-block, and four-speed trucks for example), but I also knew that nobody was reproducing them. That meant I'd have to search for one and until I found one, the engine swap would be put on hold.
Luckily, a quick post on the www.67-72chevytrucks.com forum board and I turned one up locally that was in perfect shape and completely unmolested (thanks Adam!). With that, I was satisfied that I could now move forward with the swap and not have to worry about running into any clearance issues as the high-hump pans are a good 2 inches taller from the firewall all the way back to the cross sill support under the bench seat.
Installing the high-hump pan in a low-hump truck is fairly straightforward as the low-hump floor comes stamped with a nice indentation that basically outlines the section that needs to be cut out of the floor. To be safe, I opted to drill the mounting holes first using the high-hump pan as a template, that way, I was certain that I didn't cut too much metal out of the floor (hey, it's hard to put it back!). From there, it's a simple matter of marking and drilling the shifter hole and you're done.
Making the high-hump upgrade is the simplest option if you're faced with clearance issues on your 1967-72 Chevy truck. It also gives you easy access to the transmission from either above or below, so if you've got an old sludge box that constantly needs fettling, no longer will you have to lie on your back in the rain to fuss with the transmission.