Not 100% sure on Craig's set-up, but as for the IPRA rules............

Control Tyres - Yokohama A032r
Gearbox's are free.
Diff is free
Must run Glass...no perspex

Suspension mods......difficult to answer in on sentence...however - must run original config (ie coil where coil springs are fitted and leaf springs where leaf are fitted from factory.

Macpherson struts are free. Lower control arm must be standard, redrilling of location point for Lower Conrol arm is ok if done within 45mm radially of original. Adjustable stut tops are ok. Shocks are free, as long the number and location are not changed.

Minimum ride height of 100mm excluding exhaust.

Does that help?

I should also be on the same program...in the over 2L race with teh Sunny, hopefully next weekend.