Here’s the “heads with valves” vs the “bare heads”.

With the bare heads the seats are left uncut.
The ID of the seats/diameter of the bowl where the relief cut ends/OD of the as delivered 45* angle that’s made into the seat insert:
In - 1.970/1.770/2.100
Ex - 1.575/1.420/1.700

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68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads