The entire layout of this vehicle (new body, new powertrain, new suspension) is centered around this single point. This is the only static measurement in the entire build: where the front cab mounts attach to the frame. Everything else is variable to the design.
But what if you don't like these mounts to start with?
My problem with them is that they extend below the frame and are riveted on. The leading edge of these mounts is the major limitation in tire size on a 70's F-series truck (if you're not hesitant to cut the fenders).
There are 3 reasonable options:
1) Jack the truck up with a big suspension lift to provide more clearance between the tire and body mount. I object to this due to the sacrifice of handling and stability involved with greater vehicle height.
2) Move the body mount back to provide more clearance between the tire and body mount. I don't like this idea because it will extend the overall length of the rig.
3) Move the front axle forward to provide more clearance between the tire and body mount. I am incorporating this idea, as well, but modifying the body mount allows me to alter the wheelbase by a more reasonable amount (which will also allow the tire to be the first point of contact at the front of the vehicle for a 90+ degree approach angle, which is one of the design goals).
Obviously, you could entirely alter the way the body is mounted (move the mounts inboard, etc), but the cab portion of this mount is a major element that I want to keep in the end product.
So, here you can see where I removed the mount, welded the actual 'mount' in place inside the body mount, scalloped the bottom of the mounts significantly, capped the mounts with 1/8" steel, and welded them back onto the frame.
I've also attached a photo of all the stock crossmembers I cut out.