The a500 swap is near!!! Could use advice

Hello. The 318 and 340 engines were internally balanced. (I am not 100% sure about the cast crank 340's but most all of these engines were internally balanced). The harmonic balancer and flex plate on these engines were neutral balance, ie. no counterweights etc. The 360 on the other hand was externally balanced. They used counterweights on the harmonic balancer and the flex plate. Depending on which engine you use, you will determine what you need. Summitt Racing is where I bought my last one. Some of the techs there know quite a bit about Mopars. Ask to be directed to one of them if you need to.
I hope this helps!! Todd