All of the later [short stroke] A13's that I know of [3 of them] seemed to have an engine number that followed the format A13 xxxxxx A. I suspect that the 'A' suffix denoted the second [short stroke] type of A13. The long stroke version seems to have been for the US only & was a 1974-only offering.

This is the back of the cylinder head of my A15, but is typical of A15, A14 & long stroke A13.
The tall deck/ long stroke engines are about 5/8" or 15mm taller than the short stroke ones & it's most obvious here.

























This is the back of my short stroke A13 block. It is typical of all 1200, A12, A12A & s/s A13 engines. [all had 70mm stroke & all these cranks are interchangeable.]