If the internals are K2-K6 and the cases are F2/3 you have some issues, like the shaft that holds the countersprocket that is held by a wider bearing on the F2/3, K7 engines. What cylinder/head combo do you use? Maybe some work in that department too. Be sure everything is alright, would be a shame to damage these, very nice, parts.
With all the knowledge here it should be no problem getting it alright.
good luck.
Rob