I'm just finishing up an LSX swap myself. There are a few things you'll run into. The LSx engines have a different bolt pattern on the crankshaft so it will take a different PTO. I couldn't get anybody to understand this so I ended up having an SBC PTO redrilled. Also GM used 11mm flywheel bolts. This is an odd size and it proved impossible to find any that would fit in the countersinks on the PTO. I ended up tapping my crank to accept a 7/16-20 bolt. You'll only lose abot every third thread so as long as you have enough threads engaged you'll be fine. You'll probably have to use a shallower oil pan (F-body or a C6). As far as exhaust, I run OTT headers and fortunately Schoenfeld is a local company. They were able to modify a set of sprint car headers to work. There is also company in Australia that makes marine exhaust manifolds for the LSX. The cooling system was easy, pm me an email address and I'll send you some pics of what I did. You can also get away without O2s and MAF. If you have any other questions I'll try to help in anyway I can.
**Edit**
This was on a jet so if you're running something else then I don't know how much of this will apply.
**Edit**
This was on a jet so if you're running something else then I don't know how much of this will apply.