After a lot of tooing and froing I'm gonna go with NA..
The chap I bought the engine off had pics of the engine with head off and the pistons were stamped 0.5 The crank is scribed GGR so they may have done the rebuild.
Once I get the head off again I'll measure the bore size and take it from there.
I'll check those numbers by the dizzy too.
Thanks for your help! I'm gonna need loads more LOL!