[Rory McNeil]

I have not checked the Guide for a 75 Ford, but I seem to think that the 351Ws had 1.84 & 1.54" valves, up until about 77 or 78. Also, with a 2 barrel carb, the 351Ms larger valves won`t have much benefit. Depending on what chassis you are looking at, the 351W engines came in more models, the 351M was mainly full sized cars, and PU trucks and vans.
With the 74 Ford 460 smogger engine rather popular in S/Stock, one has to wonder how it would fare in Stock. All pretty heavy cars, but a 460 cube engine at 300 HP.....