Scroll through the threads here and read anything that says "390.." and "360.." and especially "360 to 390..." A 360 is a 390 with a 352 crank. Or, an overbored 352, depends on who you ask.
The failing of the 360 is low compression. 390 crank and rods fix that problem. A little cam, a good intake, headers, 600 CFM carb--almost double the power, same mpg.
Threads like this:
http://www.ford-trucks.com/forums/72...his-combo.html
See the posts by FalconStng, exactly what you need to know.
As for heads, aftermarket heads for the most power, cleaned up stockers should be good for econo build.
Read on & good luck.