I weighed a Nissan vg30et at 152kgs with flywheel, turbo, water pump and manifolds. That's light for a 3 litre that can develop well over 400 WBHP with stock internals after turbo, fuel and computer changes. It's also a small package. There are factory bell housings that bolt up to the T5 gearbox which is probably the most common box in the world. That box also offers lots of after market options for c/r gearsets too.

https://www.youtube.com/watch?v=QuC9E3H6FH8

https://www.youtube.com/watch?v=j0Coaz2bMXM