Oil leaking from rear main still

I am new to this site and have a problem with my 65 econoline 12 window. It has a factory 170 with a c4 auto. trans. I sent it to Jasper from Oregon to be rebuilt, got it back, put it in and right away had a leaking rear main seal. Long story short, it went to my local mechanic twice under warranty for new seals, both kinds were installed and it still leaked. I r/rd the engine three times myself, back to Jasper in Indiana returning with the same results. Nobody could figure out what happened, never leaked before. I got a complete refund including my labor and fluids for a total of just over 5k. I have a freshly rebuilt engine that runs perfect but still leaks oil. It has been determined with dye to be the rear main seal. It has a clear puke tube for crank case vent, but found a plugged up oil breather cap which i have ordered. Any thoughts on how to stop the leak or maybe just get a 200 six?

Gosh, with three seals on a 'fresh' motor you must be pulling your hair out. The plugged breather certainly isn't good. If it wasn't a new motor I would look at some serious blow by. Just for grins, I wonder what a compression check would show? I had a similar experience that turned out to be broken rings. Good luck!!

That is one crappy experience! If you have to start over I would go with a 200.

B4 that I would C if the main can B changed (if every1 is sure that's it). Gotta get a definitive diagnosis...
It CAN be changed w/o another removal…did they use the modern composit (& remove the lill pin)? another rope?

Let's keep at it together awhile.
PCV OK?

Failing to remove the pin in the rear main is a common oversight even by the pros. I've seen it done many times even in the 289/302 engines. Another thing i've even seen done by rebuilders that switch from rope seals to modern seals is they install them backwards by mistake. Three times in a row seems remote, but don't overlook the obvious either if you start taking it apart.

"...install them backwards by mistake…"
lip 2 the inside is correct?

U can jack the motor away frm the transmission, drop pan & main caps, lift crank & do seal frm there.
This pin mentioned is @ bottom passenger's side I believe.

Keep talkin...

The pin is located in the center of the lower rear main cap. Either remove it completely & fill hole with RTV.
Second choice is do nothing.
Third choice is shorten the old pin & reinstall enough so it will not interfere with the rear main seal & the pan lip seal. How dry I am.

Sounds like you've looked at every possibility, so I feel stupid for suggesting this, but if the flywheel (or flex plate) bolts aren't sealed, oil will leak out and look like a rear seal. I'm sure you've eliminated the rear oil pan seal also, but for some reason the new Fel Pro rear pan seal seems a bit too long, and can cause problems.