I could be wrong, but I thought that bassani used a x-pipe that fit to the factory headers. At least for the 01. I thought I saw an ad in a 5.0 mag w/ long tubes for the 4.6s.
The Bassani x-pipe will fit the stock manifolds or any shorty headers like JBA's or FMS. Buy only JBA's. They get numbers nearly as good as LT headers. FMS headers will net only 5-6 HP. Not worththe effort. If you run LT's then you will have to run shorty h-pipes like BBK's or VRS makes a shorty x/p. I've ran all of them. Bassani is designing a mid length header and x-pipe right now. I have a catted Bassani and catback on my 03 right now. If I do headers, I'm going with JBA's.