I have been getting a flood of calls from guys with 1965-1966 F100 interested in a new IFS kit. The conversation goes like this: “I want to put in air bags and lay the rocker on the ground with my 65-66.” Simple enough request I suppose. Not new or original by any stretch, but here is the lowdown for you guys, it’s not easy with the truck you picked to build. Building a 1964 or earlier would simplify the goal so much more.
My kit will require a dropped spindle and to Z your frame at least 3″ on those trucks to get the frame on the ground. But you will miss your mark by a few inches as the frame extends below the rockers on those trucks. You will also have to tunnel the engine and trans up into the floor to get the oil pan off the ground. Even in the 61-64 you will have to do some floor modification. My 63 uses the 4 speed trans tunnel to clear the transmission and I had to notch various and assorted crossmembers, relocate parking brakes cables and such for the drive shaft to clear everything properly.
It’s a tight squeeze everywhere!
The first image that came up on a Google search was this, and you can clearly see the frame below the rocker just behind the wheel. I bring this up because recent callers have taken me to task about this issue stating that their frame does not protrude below the rocker. As you can clearly see, it does. If your goal is to put the rocker on the ground, this is a problem. If you can accept the rocker a few inches off the ground, then this is a non issue. From my professional standpoint, no part of the body or frame should ever touch the ground. Any highway driven vehicle should pass a minimum scrub line test. I know it’s trendy to do this, but it also frowned upon by government institutional authorities and the like.
Ford made quite a few changes in 65, most obvious was the switch from beam axle and parallel leafs to the twin I-beam and coil springs. They also changed the firewall and floor to gain much improved legroom over the earlier trucks. They also raised the steering column up into the dash slightly for a much more comfortable ergonomics. It’s that extra leg room that is going to cause you guys grief. The frame had to go down to make room for your legs…
Most likely will have to either section your frame which will weaken the frame, or channel the body over the frame to close the gap on those last two inches.This is not a minor task. Your best bet is to install a straight section of frame rail and fabricate a whole new floor to cover everything back up.
Just don’t tell anyone you got the information from me 🙂