FWIW I didn't read every post/comment so this may be repeat:
Personally I would say if you've lost interest in the Supra build (and already have a buyer!) sell it. If the GSXR is now an afterthought, sell it.
DD the truck. Get a toy whenever something strikes you using the Poopra/GSXR monies. Pretty basic. Maybe pay off some debt.
IF you want a C10 or something similar you can certainly do that. As for long beds riding better? Well, Elliot ('78 K10 short bed) rode pretty well. EllIIot ('82 Ford long bed, a.k.a. Cleetus) came with cut springs and one of the rear leaf packs resting on the bed. Do your homework. (Yeah, a friendly jab at Clay was inserted here. )
If you just need a truck for hauling/fun I 100% support ditching the ram for an older C10 or something similar. Personally I like the older gen's with the round headlights the most. EllIIot DEF gets attention almost daily. Everywhere I go SOMEONE asks about her. Maybe get an old pickup then a reliable DD that's good on gas.
And no, old vehicles don't cost a lot to repair and parts are NOT hard to find. Maybe for a late 80's Supra or Fiero, but these old trucks have MANY options for each part and everything is stupid easy to do yourself...and I'm not even a licensed mech like you.
Best of luck bro.