91Mustgt4me

Hey guys, I'm in the market to get a new car and am debating between a 5.0 (94-95) mustang or a 4.6 (96-98). Here's the deal, I want to make it faster and know buying a 5.0 would probably be cheaper but i have been able to find decent deals on a 4.6, and for some reason i really like the smoothness of the new engine. So here's my question, say I could buy the same exact car, mileage and everything for the same price but one was a 5.0 and one was a 4.6, which head swap would give me the most power? Would swapping new heads onto a 5.0 get me more than swapping the newer (99-03) heads onto a 4.6 and which would be less costly. I'm thinking buying a 5.0 and putting those thumper heads with a different intake/headers/etc. would be cheaper and net more power then the same thing on a 4.6. Lastly, which engine would turn up better mileage day to day, since it'll be my only car. Thanks for the help in advance.