Don't know about rb26 v rb25 rocker covers but 33 engine mounts are too high for rb25 crossmember and engine mount brackets.
Can you get your hands on old mounts and measure them?
Ideally harness bar.
But...
Seatbelt buckle anchor on seat next to centre console. Other side on seat belt anchor
Then use seatbelt buckle anchors on rear seat.
Rear main seal is a decent job as you would know.
Make sure it isn't just the cam cover leaking etc and running down the back of the engine and bellhousing
Even take it up to a shop and get them to have a look/let you have a look.
I gathered Cusco would have better rose joints. Just hoping someone new if one was stronger then the other as the cusco ones brake easy enough when rallying.