I have had my Cougar V6 a few months now and would like to sometime in the future upgrade the engine. I would like to go for the 3.0 from the st220 as it should fit without too much trouble. I am just wondering though what all is required. Do i need the whole engine or will the 3.0 block and the 2.5 heads be sufficient? Will the ECU in my cougar work with the conversion or will a 3.0 ECU be required.

I have thought about the st200 engine but wondering if its worth it when the 3.0 will be as easily done(possibly)

Really only starting to research this so any advice would be gratefully appreciated. Thanks