I know what Dave and Bob are saying, but looking at the fact that you are in Britian, I'd say build the FE (course I am partial to FE's). Either way you'd get a lot of torque but as I read you're not looking for a racer, but a street vehicle. That's why I say build the 390. You'll like it. Plus you'd already have a good Tranny and rearend to go with it.