Cheers for all the info!
Firstly, the car's a carby fed, 5 speed manual. Rear LSD sounds good, and I'll probably pick one up and do the rear disc brake conversion at the same time.
Does the RX have different gear ratios as well as the diff ratio??
Also, how difficult would it be to install the centre diff into my car (if I could locate one), and would it be worth it? At current I just drive it in FWD unless it pisses with rain or I hit the dirt - this is fine, except it tends to lift the inside wheel when cornering (which should be cured as soon as I invest some money in suspension...)