My engine builder is looking for an alternative rear main seal for a 302 GMC.

My engine builder wrote.

Has anyone found a rubber 2 piece or full round seal for these motors? I have had 2 BEST gasket seals leak on me. Any help is appreciated. I'm not blaming Best gasket, never had one fail before. The second one leaked worse than the first.

I heard that FelPro makes one for the 59 block but not before. Any guidance or input is appreciated as removing trans,driveline,clutch,flywheel and dropping the crank didn’t facilitate a repair. Does the front sheet metal, radiator etc have to be completly removed again to remove the front timing cover, harmonic balancer to drop the front main bearing on the crank to help feed another seal?

Lots of work and money so far but need the oil leak fixed . Please help!