Have short block 340 and need the rest

I did the same exact thing quite a while back. If your going with some aluminum heads and aftermarket intake, all you need is a 318. The balancer is correct for the 340, and there’s a lot of stuff in there you might not think about. Such as cam retainer plate, oil pump bolts, timing chain oiler. It’s a lot cheaper and easier. I went real cheap back when I put mine together and also found a 360 for all the top end. A set of 596 heads works real good. Just plug the air holes, and plug the egr on the intake