All I can say is I'm glad my 460 experience was with an '85 with a carbuetor! I never thought I say that. That rig was the biggest turkey I ever owned. I was seriously considering getting a 4-barrel Holley carb like my '71 Colony Park wagon had, and disconnecting all that smog crap. In small-town WA we don't have emission tests, even yet.
In the end, because we hated the floor-plan and a bunch of other things, we sold the rig, at a substantial loss. Six years later we bought an '02 Class A (32') with the V-10. What a difference - no degradation in gas mileage with altitude, no spitting and banging when the cruise control disconnected and 35% better gas mileage in a bigger rig. Sometimes "almost vintage" rigs aren't worth the trouble.
Based on our experience, I wouldn't touch anything between about 1973 (before major smog gear) and around 1992, when everyone had gone to EFI.