Just like the title says. Only requirement I am looking for is for it to already have a drain plug. Increase in capacity is a plus and so is a proven design that decreases temps. Any suggestions? Thanks.

 

Based on the finned design, both on the outside AND the inside I would drill and tap the housing or OEM cover.

 

Not so sure this will work that good. When I changed my rear axle oil I was thinking of doing this, but looking at the lower location where the drain would be in the cover, I believe it would still leave at least a cup or more of oil in the diff. The drain would be just a little to high in the cover. Even taking the cover off completely leaves about a half of cup of oil in the diff. It is probably better to take the cover off and us a clean rag to wipe the diff housing out completely. This is easy for me to say though as I have a lift in my shop, which makes if fairly easy to do this. If you had the car lifted by the rear only and on jackstands, the oil left in the diff would be even more. I had a TA performance cover on my 06 GT and that had the drain located in the lowest possible location. No real cooling benifit though compared to our Boss factory covers.

 

My 9" in the Falcon has a hole in the bottom of the housing that is tapped and plugged. That is the best way in my opinion if you don't want to have to remove the cover to drain the fluid. I don't think any aftermarket covers have the fins on the inside like the Boss does. That makes the heat transfer that much better!