It sounds like the OP has a cobbled together combination after reading back through the post. Back in my earlier days, these were referred to as "grenade" engines. They weren't built for longevity, they were built to only make one or two all out passes. My suggestion would be to make sure that the builder didn't have the reciprocating parts balanced, first. From there, if it isn't balanced get the casting date of the block and then get the correct balancer, flex plate and converter. As I stated earlier, continuing to drive it is going to get in your pocket big time when the engine eats itself from improper parts and pieces.