I read that the old trans can be put behind an lsx engine. Do you need an adapter or are the dimensions the same you just need to drill and tap the one hole? If this is the case can you use a flywheel from a one pice rear main engine or are they balenced difren't. finally if I would be able to do this would the cross member still line up.

Another question does the truck ls oil pan fit with the tubular k member.

 

I forget the details, a should bring it up, but the distance from the crank face and bellhousing mount is different on the LSx engines.

Truck oil pan won't fit with a stock 3rd gen crossmember. Not sure about tubular, probably varies with the specific tubular supplier.