I have a 292 in my 78 GMC 2.5 ton. It used to be an Asplundh chipper truck. I installed a cast iron header set fro Langdon's Stovebolt and a pair of carburetors from a 1979 Honda CX 500. The performance level is fabulous! The I added a Brownie behind it. If you want to keep costs down, get performance and mileage, I'd lean toward building a 292 from the bottom up. The intake would have to be custom if you want to retain that updraft, though.
Even if the suspension will take the weight, you'll be asking more of the brakes than what they were designed for. You'd also want to put a sway bar on it in a big, big way!
