In no order
Bodywork tidy up
re bush 90% of the suspension
baffle sump
try and come up with a hydro system that idea is dual caliper and keeps the cable brake
Decent exhaust system
more adjustable arms with a GOOD geo
Roll cage
Aftermarket Diff
New wheels if there enough budget but then i bet only 50% this actually gets done for next season
Edit; more arch liners