any nova .21 sleeve will fit and work .7bt-n21p-367-5t-5kt you might get more bottom from one sleeve and less from another or more top end and less from another but they will all work in the end.
5kt more bottom ,367 bottom and linear smooth top ,5t more bottom ,7bt more top but they will all work it's just what you looking for out of the engine
the crankcase's are all 3 port crankcases no different from any other .