78' 360la rear main seal and one pc. pan gasket?

Looks like my rear main seal is leaking. The engine has to have less than 2k miles on it as its in my 88' Jeep wrangler.







It gets a lot of abuse. While at the dunes it will see 5k RPM quite often. Is it possible due to the higher compression and high RPM that the seal got weak and started to leak?

Whats a good seal to go with, and also I see they do not make a one piece pan gasket for the LA but they do for the magnum. Will a magnum pan bolt to the LA block?