now youre talking my language mate! ha ha!
what size are you running now?
the supposed ideal for a 33, is a 195 50 15, but this includes road use, so a track only car can benefit from deviation form the so called ideal, although this size does work very well, if used alongside very well set up chassis and suspension.
however, if you want to increase your final gearing aswell, a larger rolling radius and stiffer sidewall would make great sense, so the use of 16" or 17" rims, with 45 or 40 profile rubber respectively will help all round.
a 195 50 15 tyre has a total rolling radius of 576mm
a 195 45 16 tyre has a total rolling radius of 582mm (+1.04%)
a 205 40 17 tyre has a total rolling radius of 596mm (+3.47%)
clearly theyre are many inbetweens but these are common and cheaply available sizes so i thought we'd start there.
if that doesn't sound like it will make enough of a difference, then maybe its simpler to fit a later gearbox.
is yours the fabled 1200 gearbox, or the taller 1500 type gearbox?