you can do a number of things, all depends on budget,

a14 internals inside a12 block.
oval port head & double valve springs, ( h89 or gx ported ).
big bore 76mm
higher comp makes better power/torque. (if combo is right)
nice cam. (dailed in).
good extractors & exhaust.
electronic dizy.
go around carby. (eg;32/36 jetted)
list go on.
heres some examples of what could be done.

i've got most things in stock or can do, if that helps. cheers