harmonic balancer

Quick three questions (maybe more ??'s to come.. lol). Putting a 318 magnum (1994) in a older car. Which harmonic balancer do I use (or does it matter): The magnum balancer or the LA balancer. The LA v-belt pulley system will be used, along with the LA timing cover. Second question is this: I have a roller cam from a '89 360 TBI. It has the longer snout for the mechanical fuel pump eccentric. I also could buy the 20 dollar kit from Hughes and stick with the magnum cam already in the 318. Which is the better choice, and which would give better performance, or horsepower? I realize the 360 cam is set for 1.5 rockers, so installing it in the magnum with 1.6 rockers will give about .030 more lift. Third question is will the LA 318 flexplate work for the magnum? It is being hooked to a 904. Thanks...

P.S. I have a lot of "I thinks", I'm looking for someone that "I knows"... lol :D