So how besides the leak do you know there is lots of block pressure? I agree with the cleaning the breather box, hoses, replacing the o-ring on the breather box and the dipstick and trashing the flame trap line of thought.

If you have the chrome oil cap, have you done the teapot rattle test? If you loosen the cap so it is loose and ready to lift off, what does it do? If you have excess pressure it should start rattling like the cap on a pressure cooker, if you do not it should just sit there. After my before BB days of an epic massive oil leak from a clogged flame trap. I do that test at least once a month. Now running full synthetic oil, have a clean breather box, relocated flame trap, and that cam seal holder in place.

The reason I ask (and you may not want to hear this) maybe the rear seal is the culprit? You would hope not, and I would start with the breather box and hoses first. But you may want to keep the possibility of the replacement seal being the issue.

Good Luck,

Paul