both my zaf50 and zaf80 are gt5a but i disagree
. they both are 38mm stroke i believe. 40mm inlets on both. large transfer tunnel.
i have seen two blocks with large or small transfers passages aswell.
i have never seen a pk80.
there is no specific engines just choices. 3-4 cyiinders. 3 rods. 3 blocks. 4 cranks...... 4 pistons. 5 heads etc etc.... when buying the grubee's anyway.
the pk80 i dunno.....I dont know how may ways you can build the 40mm stroker....
--WARNING I COULD BE WRONG--