The early 99 fits only that.
The L99-2003 is even more difficult to build a mount for, the exhaust housing has a Marmon clamp to mount to uppipes. .84 housing wastegate stock. If I had a choice I would go a different way. However If this is a run what ya brung type of deal, I have seen creative folks with crazy fab skills, lots of time and a very low budget pull off some amazing things!