If you're keeping the SM-420 4 speed, you won't need a crossmember under the back of the transmission. For the under-the-bellhousing crossmember, put an ad in the "parts wanted" forum and see if you can find somebody who has converted a V-8 truck body to a later model frame. They might be willing to make a deal on the crossmember you need. The 48 crossmember won't accept the V-8 bellhousing mounts. Up front, you'll need an aftermarket tubular crossmember to adapt to the side mounts on the V-8.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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