[Billy Nees]

Well it looks like either way you go with the 390 you are going to have to write a letter! The big cars list a 315 motor and can't run the big cam or the Holley carb( lists flattop) but NHRA has given them the HP hits of the 320 HP Mustangs. Older 390s with flattop carb have an NHRA factor of 280 HP. OR, request HP back on the 2V combo. It's not a small 2V and using the older 280 HP combo as an example you might be able to get the 2V defactored to 230 or 240. Now that sounds like a "Dime Rocket" to me!
Either way to do the 390 you've got to write a letter and make some phone calls.