Does anybody know what engines will bolt directly into a GK76a?

Also does anybody know what heads will fit a GK76a?

i own a gk73a i think they are very alike just different frame not 100% sure worth checking though

AFAIK, the GK76 chaned to a different frame style, whereby the engine is integral to the structure, rather than just sitting in the frame.
I'd guess that would require any replacement engine to perform the same role, or at least leave room for more structural work.

believe it or not but the 750 pre sling and slingshot motor will fit in the 400 gk76 frame with out cutting or wellding! i have seen it done before and i will be doin it when i get another gk76.