Engine swap issue - any advice?

I have an 89 vert that had a bad rod. We are trying to swap in an engine from a 83. We had to drill one hole in the head for an intake bolt, but that is not our issue. The engine does not want to nest with the transmission. They were very difficult to get together and once they popped in, the engine doesn't want to turn over. It will turn over, but it is VERY tight. Loose from the transmission, it turns normally. WE are using the 89 auto tranny, torque convertor and flex plate. Were there any differences in the crank that would cause a tight condition?

Thanks,

Bob