Just picked up this DeSoto with its original 291 hemi that spins free, all chrome looks brand new

Planning on keeping the paint as is just protecting it, no rust at all (Utah car) and the frame still has paint on it. Has its 291 Goldilocks hemi. Thinking about finding a 331 to put in with an adapter for a 5 speed, and just raise the compression from 7:1 to 9.5:1 with domed pistons and a cam. Although this motor is a factory four barrel, maybe I'll do those things to this. Don't need it to be fast, but 150hp isn't a ton. I'd like 300 at the crank.

Floors are solid, dash looks great, I've found glass already.

Anyone have any other ideas on what to do to it?