Talk to Ken at Cycle exchange.net
My list.
$6,000 cash limit? dreaming...
Different cam
valve springs
Valve spring retainers
Rocker arms lightened
Special engine parts coatings
Crankshaft modifications
Stronger cylinder head studs
Camshaft cover stud modification
Exhaust and intake modifications
Basically almost every part of the engine that can be improved
On a Roadstar Adventure.