I pulled the rear main seal to replace it 4,000 miles after what apears to be a paint can rebuild. Never turned the crank just slapped the new parts in. Rust pits in the cylinders and everything. What do I do, it looks to be $1500 to just rebuild the motor. The rebuilder was telling me that he has seen the heads crack and the top of the cylinder blow off on these motors. Is he just full of it or should I get a new SBC and throw it in?