[Brian]

These pictures are of a 36 LB rear main cap, like yours, that I modified to take a positive seal. I had to grind the slinger off of the crankshaft obviously. The insert that goes into the block is changed to a later model style that accepts a rope seal. But, see how I screwed it into the rear face of the cap? You could do something similar but with the same profile as the 37 insert in your possession. Good luck!