I think we're all saying pretty much the same thing, Jeff.
To optimize a post '57 FoMoCo y-block, consider heads with bigger intake valves AND more compression ('G's or 113s would be ideal), consider swapping to a '57 and up 4 barrel intake manifold (some post '56 HD truck engines used these on 292 engines), and install '57 and up exhaust headers and dual exhaust pipes to the rear. Yes, the '56 or '57 1.54:1 ratio rocker arms would be good to use, but they're getting harder to come by; all the other year y-blocks before and after '56/'57 used 1.43:1 ratio.
NOTE: While they breathe GooD, I would not install 471 heads (vintage '59 312 Merc and '59 Ford 292 truck) with their large 'G' and 113 size intake valves because their combustion chamber size yields such a low static compression ratio. The 471 heads coupled with a performance camshaft that keeps the intake valve open well after BDC will produce a dynamic compression ratio below 8.0:1 which will negatively curtail low speed performance, throttle response, and low speed drive-ability.
IMO, THE most significant performance killer on the post 1957 y-blocks was FoMoCo's installation of a camshaft with less lift and duration. This was an intentional move on Ford's part. They wanted to sell the new '58 Ford application 332 and 352 big blocks which became the 352, 390, and 406s in the early '60s. Consider swapping to a Y-265S camshaft from John Mummert OR talk to Ted Eaton about his recommendation for something made-up for your transmission application (standard or automatic) by Iskenderian.
Scroll down through this web page of John Mummert's off-the-shelf offerings and notice the significant difference in lift and duration numbers between a replacement y-block stock camshaft and JM's beginning performance offering. Click the link below...
http://www.ford-y-block.com/valvetrain.htmAgain, ALL of the items mentioned by Forum members have a definite role in how your engine performs, BUT if you change the heads, the intake, and the exhaust and do not install a healthier camshaft, I think that you'll be disappointed in how your efforts are rewarded.
Hope this helps.
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York