The 4.6 DOHC would be cool. I was under the impression that these motors were a lot more expensive that that. Last time I looked they were around 6k to 8k. If you can get one for 2700 that is cool. Make sure its not a SOHC. The 4.6 is wide, wider than the old FE motors even.

Have you thought about a 87-93 fuel injected 302. After-market is huge, and the installation would be simpler. I get usually knock down around 23 to 24mpg and can run 10s at the track. Also the 302 is much simpler to work on than the 4.6.

buts that my .02