Frank, while there are many on the forum who seem to abhor old engines and will recommend only OS .20/.25 FPs and such- fine engines no doubt- for older .35-size models, your McCoys will do as well as they did in the '50s/'60s.
There are also a few who love the old engines, including McCoys, and fly them regularly.
Perhaps they'll pipe in with helpful insight.
Meantime, be sure to run 25-28% oil (preferably 50% castor) and, they being iron/steel, "heat-cycle" break in carefully.
Sure, you won't win contests, but sure, you can have lots of fun.
regards,
Terry Caron