I don't have anything that I intend not to build, but I don't have anything near as rare as you do either. Probably the rarest kits I have are two Transtar 4070A kits and while somewhat rare and unable to be produced again due to tooling changes they're not exactly hard to find if you are willing to pay for them. Fortunately I got mine a couple years ago when they were a bit cheaper and bought them with rough boxes so I didn't have to pay mint prices.
There's nothing wrong with using the short hauler frame for a tractor. The only thing I would do is hold off mounting the front axle until you get the rear on and some tires on it to make sure it will sit level. With the thicker frame and borrowing a rear tandem setup from another kit you may have to put a small block between the spring and front axle.
I'm definitely an average builder, a lot of the builds here make me want to take all my stuff into the yard and set it on fire. I really just build to satisfy myself though, if I try to make everything perfect I get bogged down and end up abandoning the project. I build each vehicle as if I owned it and would build it myself if I had the money so each model has custom parts and things borrowed from other kits which makes them more challenging so I frequently hit stumbling blocks that stall projects until I can find a solution.
Thin wall aluminum tubing is incredibly hard to bend sharply, get some 6//8 or 7/16 inch stainless steel tubing that is 1/16 wall and use a real tubing bender or a wooden buck to bend them. You can use a grinder to thin the open end to scale thickness once you get the bends made and polish to your desired finish.
It totally depends on the opacity of the paint and the number of coats to get the desired result. With older Testors paints that are fairly thick I can usually get two cars to a can with a tiny bit left over, with the newer lacquers and some Tamiya paints I'll use most of a can easily.
I remember reading in another post that the NHRA rule for gassers specified that the crank centerline could be no more than 24" off the ground so the massively jacked up noses are more street mimicry than actual race legal cars.
Yeah, Clayton's mounts look super custom and I will definitely use them on another build but I'm kind of already down a path with this one so I'll have to use something more like the aluminum bars this time.