Correct motor and transmission mount set up

[Cgoldhill]

Just looking for confirmation on the correct mounting set up for my '72 Chevy C10 long bed as I'm trying to diagnose a potential bad rear main seal. I swapped a Muncie in over a year ago and at time of install there was no rear transmission crossmember so I purchased a new one and installed it with a new rear mount. The truck was originally equipped with a Saginaw that used the bellhousing mounts. My question is should both the rear transmission crossmember mount and the bellhousing mounts be used or just the rear mount along with the 2 engine mounts? Can using the both sets of mounts for the transmission cause any driveline angle issues?

At the moment I have the rear transmission mount, the bellhousing mounts and engine mounts all attached. I'm having a serious oil leak issue coming from the rear that looks like a rear main. My thought is by having both the transmission rear mount and bellhousing mounts attached its pulling the transmission down at enough of an angle to create a gap in the rear main. The bellhousing mounts themselves are in pretty bad shape and very squeeshy. The rear main was replaced about a year ago, not at the same time as the Muncie, but was performed by a shop and had no leaking issues for some time. A few months ago I noticed the bellhousing mount bolts were pretty loose so I tightened them up. It seems like not too long after I developed this leaking issue. At first I thought it was a bad oil pan gasket as I know the shop had replaced the main ( or so they told me). Replaced both the pan and gasket with a one piece fel pro, made sure I had the right thick gasket, etc. RTV in the corners, torqued properly, waited 24 hours for rtv to dry beforing filling and running. Pan bolted up nicely but the leak actually seems worse now after start up. It won't actively leak at idle, only when giving it the business. When I say leak, I mean its pretty prominent. After a good full throttle run oil quickly collects around the starter and backside of motor and drips on the passenger side. I've also replaced the valve cover gaskets and distributor gasket in the past.

This is a supercharged 350 with about 100k miles on the rings. Considering the motor still runs great and don't have issues with performance, I don't think the rings have gone so bad that I'm pressurizing the crankcase at full boost. I get alittle smoke on initial start up from probably leaky valve stems but no smoke while driving or under boost. It also has a breather on one valve cover, and pcv valve properly routed to a catch can and a good vacuum source on the other side.