Just get you a 390 or a 428 if you want to spend a little more money. It's very easy to get 400 hp out of a 390 the factory did it. The FE will run very well with factory parts or the aftermarket makes some very nice pieces as well. The first thing you should do is find the casting numbers on the heads. Since you're putting the motor in a full size car there are plenty of factory heads that can be had cheap and make good power and work in your car. Just about any FE head from 1960-65 will bolt on to your car and make good power. The 427 Low riser heads are basically just early 390 heads with bigger valves. So don't pay big $$$ for so called Hi-po heads or Cobra jet heads or anything. If you want to go cheap you can find you a 390GT intake and it'll work great for making your power goals. The down side of it is the intake weighs a ton and you could save a good 75lbs by going aluminum. If you want a mild build up thats cheap go with a 428cj cam, and some headers. This combo will make you at least 350hp. If you want to you could step up to bigger cams and make some big gains. I'd say get us the casting numbers off your heads and mention how much you want to spend and it'll be easier to make suggestions. In my opinion it would be silly to do anything less than a 390 though.