Out with the 318 in with?

IF all you got is around $1,000 then just refresh the 318. it still be tough to do at that price.

To keep costs down I would use all those parts you have and get higher kb compression pistons.

400 hp can be had out of the 318 and today higher compression pistons are out there.

you need to decide cause 4.10 gears and a 4 inch stroke crank is not a good combo for longtime use. Personally I would never stick a 4 inch crank in those small blocks unless maybe you got an aftermarket block. Why not just get a big block motor if you want 400 plus ci ?Get a block that was design for the longer stroke, IMO