having a 1969 4 bolt main 428 built for my 1965 GTO. motor was stroked. Been at engine shop 1 year. went with all forged internals, new crank, rods, pistons, KRE heads, roller rockers, RPM manifold. all done to the tune of 9K. engine just went on dyno and was informed the rear main was leaking bad. he said he used the new neoprene seal. Engine has to come down now to replace seal. He does a lot more chevy motors than Pontiacs so not sure what his next move is. any suggestions?