Want a giggle ?? After pulling the box and finding a dry rear main I put it back in, for the next 5 days I replaced the -12 line, purchased and fitted new AN fittings only to wake up and think, "the f*ckin dip stick hole" . I have an aluminum pan that has the tube welded to the other side, I had forgotten that we last ran this engine with a different pan. Sooooo all my oil was coming up through the open dip stick hole in the block.
IDIOT

I offset the crank seal. Put the retainer assembly in the freezer. Makes it easier to slide into the block. Put side seals on with sealant and slide it in easily
Works quite well

Welcome to the club that Murphy messes with
If you don't error now and then how you going to learn
Congrats on the find and sharing it with us

nicks garage in canada has neat way of doing rear seals he has a videdo of him building a mopar bb shows how he puts seal in,he offset the rubber by 1/4 of inch on one side,meaning he leaves a 1/4 inch of seal sticking up before install and he swears he have not had any leaks,the guy from pete garage build a 440 with same method and explains how it works.seems to work for them.

Offsetting the seal does little to nothing to prevent the seal from leaking. I’ve built at least 8 bb Mopars over the past 5 years with no offset on the seal. Zero leaks. It’s all about the alignment of the upper and lower half’s of the seal.

And offsetting the upper and lower half s helps with the alignment of the aluminum retainer itself

I got to play with this when I built my motor last winter

Aligning the seals flush with the block , crankshaft out , and then marking the retainer surface and block with a sharpie when snugging up the retainer and seeing the alignment of the seals with the crankshaft installed and out

Then tried offsetting the seal halves at 12 and 6 , installing the retainer again , and the retainer was in perfect alignment with those sharpie marks

Personally I think a lot of these leaks has to do with the side seals or retainer

I just went through this. This is what fixed it:

1.Found interference with windage tray and top of stud , drilled windage tray to allow stud to "pass trough"

2. found interference with the little 12-point nut and seal retainer, 1/2 moon-ed the retainer in the nut area for clearance.

3. clocked-seal 90 degrees.

This was a fresh engine that was run 3-4 times pulled out, sealed up, pressurized and leak checked with soapy water and held 25 psi of crankcase pressure out of the car with no visible leaks at the gasket or seal, however leaked like a sive while running. Being able to examine the pan gasket under pressure I am confident that this was not a gasket issue. My summary would be that to make sure that the retainer can float without interference , then clock seal 90 degrees so that it alignment is guaranteed, fill sides with a good sealer sealer (I have always just used sealer on the sides). I have built many bb mopars, stock rebuilds, stud applications in stock blocks, and aftermarket block builds, this was my first leaker.