Hobbit

i cannot give you specifics but the next logical step would be to make the motor strong enough to run more power.
As i understand you would need

Roller rockers
adjustable pushrods and outers
Clutch upgrade
possibly oil pump

then you could go

Cams
porting and polishing on the heads
HC pistons
big bore
Stroked motor

i'm sure soembody more knowledgable on building these motors will chime in.
i would try and do as much as possible in one go like cams/rods/heads/rockers
and save the big bore for if that alone was not enough