Sorry... don't know the differences between model T, A, and B heads.
I assume these Champion 3X plugs are indeed different than the 'single' X ones?
I am not familiar with the 3X plugs, but the seller says they are for model A & B Fords. The photos look right for that. A & B Fords use a straight thread (like almost everything else other than a model T). The model T (unless you are using some odd after-market or European head) uses a tapered pipe thread. Those in that ad are not a tapered pipe thread.
Yes, different threads, and yes, for Model A, B engines.
Very good... thanks for the clarification. Somewhere along the line, I picked up the A had the same head as the T. Obviously not!