Build a snappy 400 or if you must stroke it, do a 451. Those are common enough that parts are readily available with reasonable prices.

Skip the ported heads. You want to keep the port velocity high for cruising. Forget the guys that say you need 638 cubic inches and a 12.7" lift cam with 836 degres duration.

A set of Edelbrock heads (or similar) would do the trick. Find a cam around .500 lift with moderate duration and you can still use the stock valvetrain. It will make plenty of power for what you need.