All 460 blocks are good ones...basically most all core 460s are good ones (carbureted versions). As far as a rebuilder core, the main difference between years is in the cylinder heads, but for a street engine to 500HP or so, any year will work and be a maintenance free engine at that HP level. (More HP is certainly possible.)
If you want some grunt power for that Galaxie, I would suggest a 501 or 521 stroker. I'm not a fan of the 4.5 stroke (557 stroker) cranks for several reasons, unless there are specific circumstances for running them. These stroker rotating assembies are available complete with bearings and rings, just bring your block to the machine shop and have them prep it for assy. Also, you will be amazed at what the OEM iron heads can do when propery prepped for the application, AND when you pop the hood the engine looks like a stock longblock...and then you
smoke the competition.
Give some more detail about how much power you desire (and if it must run on pump gas) and I can suggest a combo or two.
Paul
www.highflowdynamics.com
I saw last night on fb about John. The world sure lost a great one. I'm going to miss his humor, advice, and perspective from another portion of the world. Rest in Peace Johnboy.
John Norton aka johnboy