Hi guys,
So my first question is which driveshaft I should use. I have an aluminum 3rd gen driveshaft, steel 3rd gen driveshaft, and aluminum 4th gen driveshaft. I'm going to say the steel one is out of the running for sure, but thought I'd throw it out there since I have it.

My next question is on stock LS manifolds. I bought the flanges that connect to them and the stock exaust pipe looks to be IIRC like 2". Has anyone, or is it possible to increase that size to at least 2 1/2, then step up to 3"? Or is it even possible to increase them to 3"?

 

3rd gen aluminum is supposedly heavier duty than the 4th one IIRC

2 1/2 should be doable for the flanges, by may want to do a quick check with a set of gaskets to make sure there's enough meat left to seal

 

I cut my flanges from 1/2" plate with a torch using the gasket as a reference. The holes were just under 2.5" when finished