Hey Genius. I will take a stab at this one. Finding a post 54, 235 6-cylinder would be the easiest to get her going. You can get a v-8 in there with the stock frame, but there are some clearance issues with the steering box and you will need to fab side motor mounts, and possibly a tranny mount, depending what you use. If you keep the original tranny with a v-8, you will have to find a v-8 clutch housing. The 1990 Suburban axles, etc can be installed on your frame, but the newer axles are wider than your 53 and will stick the wheels outside of your fenders. A complete frame swap is doable, but labor intensive or expensive if you hire it done. Your rear end is a 4.57:1 if it is original. I am sure others more wise than me will chime in if I forgot anything. Good luck and have fun.
Ralph
