Bruce, the short answer is, the typical old school HP engine will require boatloads more care and feeding (new bearings, new parts, valveguides, etc etc etc, ) over any given period than a current tech SM engine, or IT type engine of relatively modern standards (Honda/Acura, etc).

One reason SM is sp popular is because you don't need to be a full time mechanic that can deal with the constant upkeep and tuning issues the old cars demand.

For your SM money, you can be within a hp or 3 of the top builds for a much longer period....that same yardstick in HP will cost you time and money many fold over. That said, the level of competition in the HP type classes is generally thinner, and it's probably easier to score a 3rd in an HP car at a regional race...but...it might also be called "last".