Reading this about your Brother and Son isn't easy. I don't know if I would survive the loss of my only son, let alone try to work with a vehicle that was his after ONLY 5 years.
On to better thoughts........I'm with the others for keeping the original frame and making it what you want. That frame is strong enough to handle most any mods. I see in your journal that you want to make big power but still drive it distances. Big power and long distances usually don't mix dependably and the fuel consumption will be great too. I suggest a nice 350 hp 350 with a 200-R4 trans into a 3.08 geared axle. That's one of the most reliable combos around with parts readily available anywhere on this continent and will deliver good mileage too. An LS based engine can deliver even more power dependably with better mileage but now we're into computers and I don't like dealing with them . Many of my car friends have gone that route and computer controlled fuel injection really is the hot rod of now and the future.
Have you considered a membership in MSRA and using that as a local source for parts and help ?