I've done sonic testing on a brand new "keystone" 41-42 block - it is in my 32 Cabriolet. They are not any thicker than a new 59x 3 3/16 block (which I also happen to have). The old wives tales about the early Merc blocks being thicker - I think they are just that . . . good ole' often repeated stories - passed down through the ages.
I'll take ANY good 3 3/16 block from 39-48 - I think they're all worth using if you find a good one. There - my 3 3/16 cents for the day
