You trying to keep the car original as possible, or the build? You can get 600hp out of a 6, but like Gorn said, expect to pay out the wazoo to get it done. The 3.8 we are referring to is a GM engine, the 3.8 in the Mustang is completely different. To swap to it, you will need a new engine, tranny, radiator, radiator fans, ECU, wiring harness, exhaust will need to be modified for the 3.8 manifolds and extra exhaust sensors (if you don't want the check engine light), fuel rails and injectors, and I'm sure more that I can't think of. Oh, and engine mounts.

 

WOW that kinda killed my thoughts on the car and the build in general... So now instead of building a 600 hp car i guess i can do like 350-400 what would be the ticket on a build like that???

 

If money is a issue and you are willing to put in the wrench time. Sell your V-6 car and buy a V-8 with with an LT1 with either blown head gasket or blown motor. Buy a remanufacture LT1. Now you have a base car that can hit 350HP. You will still need to mod it but there is a bunch of ways to get there and many step by step "How too" on the internet.

If you try to hit 350hp with the V6 you will not only have to put a lot of money in the motor you are going have to replace the transmission and rear end. Anything over 280HP your going to have to update everything in your driveline if you want the car dependable..