well we've been racing our 82 4age bigport for 3yrs now and have just had the engine rebuilt for the 2nd time (got ripped off with a dodgy first time) and have just upgraded from peddars suspension to bazda coilovers. Our car also has a kazzar lsd. Tyres will give you the biggest performance boost for your buck, but the down side is the stickier they get the quicker they wear out so the cost is ongoing. For me the Advans were have been the best tyre and we've tried a few including the 888s. Our engine has the biggest cams you can go with standard ecu, extractors, bored out, h-beam rods and a smallport crank (got bigger journals). Its delievering 200psi compression and it revs out to 8k no problem. If you want it rebuilt mitch from on the forums here did the rebuild and we're really happy wth his work. Consider a 20v including gbox with lsd as i think that might be an effective upgrade as an option.