318 build suggestions?

You are basically starting out just like my project.
You will need to do lots of research and parts hunting, maybe even find a parts car. My advice is, make what you have in the car now work really good and enjoy it until you think you have everything necessary to do the complete engine swap. If anyone tells you that you should start taking apart a perfectly good working car in preparation before you have absolutely everything ready, those people are re***ded.
agreed, if the 'tuned' 6 runs well i'd spend money on the rear end, front brakes and suspension before thinking about the motor swap. re the rear end have a look at ford exploder axles. 31 spline shafts, lsd and disc brakes are stock. cut the casing long side to swap in a second short shaft (cheap as chips from rock auto) and it's almost exactly the same width as an 'a' body 8 3/4. it's a common swap that's well documented on here.
once the car's built for a more powerful motor then save to build one right, once.