Yeah good catch on the chamber size..... Unless you plan to add a blower to it I wouldnt get heads with a 64cc chamber,stick with a 58cc otherwise the motor will end up well below the stock 9.0-1 compression.
With this combo you would be lucky to come anywhere NEAR 350hp. Any more than that would require a few more cubes like a 347.
Im daily driving a Bronco2 with a Mustang efi 5.0 and a c4 auto.I run 35's with 3.73 gears and its fine for my truck and gets 18mpg .If I had an AOD in it I would just up to 4.56 tho.