For your application, the standard cylinder head configuration should be fine. A steel crank is preferred although cast would be ok with careful inspection and prep (polish, chamfer oil holes). Any year is OK except after about 1972, most engines will have a cast crank.

Beyond that it depends on how far you want to take the build. A basic solid build would use a KB 184 Hyper piston at around 9:1 cr and something like a 260H Comp "high energy" cam. If you or your shop can "fit" the KB quench dome pistons to achieve around .040" quench, it will improve the ability to run regular gas without pinging and help prevent pinging on uphill pulls with trailer. Top it with a dual plane intake and around a 750 CFM carb.