Greg!As far as I know there is no difference between the "industrial" &"automotive" -- as a matter of fact, my engine had spent the last years ina Model A! (with both dist. & mag) Being a later block, it has morereinforcement around the flywheel bearing & and some blocks also haveexhaust valve seats. The ID is a diamond casting mark between valve &timing gear cover (front end of engine in a car & back end of the engine ina Piet!
-- it's only about 1/2" long. All this good info came fromTerry Oberer (St Louis Model A Club) at the '98 Brodhead -- he was kindenough to take on a guided tour of every "A" block on the field, showing mewhat to look for. Pretty Prairie, KS is about 40 miles WNW of Wichita.Mike C.PP, KS