ztarum,
you can install a 390 now and later swap it for a 428. Everything will fit, starter, headers, intake, carb, distributor,
oil pan, water pump, etc. A bone stock 390 will have 275 to 300 rwhp. That will make a 2400 lb car fly. After you get use to flying and want more power. Get a 428 or build the 390 block. Lots of options.
Buy the book "High Perfromance Ford Engine Parts Interchange" by George Reid ISBN 1-884089-33-x $20 or $25
If you buy the correct block you can easily build a 427 or 428 motor.
Don't worry about the 390 pushing a Cobra. I've seen two or three 221 rwhp Cobra smoke fast cars at the red light.
Dwight