Thanks for the info so far guys!
Hmm, engine choice will be difficult. I suppose the best shot is the revell 240z motor with some sakatsu triple mikuni/solex carbs and a custom header, I doubt many people would quibble whether a motor is an L28 or L24 in 1:24 scale, so that would save tracking down the 280zx kit to butcher. The Fujimi 240z motor is just not particularly good IMHO so I'm not even really considering it.
That Aoshima kit looks great, just a shame its a sedan and not a coupe!
Layla's Keeper, I think you're right about the Tamiya kit. Honestly, the only reason I discounted it is that I feel I could modify an engine bay, fabricate chassis parts etc for the other kits, however I feel underqualified to produce an acceptable set of front "bolt-on" fender flares... But that may have to be the way I go I think, being an easily procured and high quality kit.
Flares then... I see HLJ have some fender flares to suit a RA40 celica, I might consider using them:
http://www.hlj.com/scripts/hljpage.cgi?S27FP2475
Unless anyone else has some good ideas on obtaining or making some, which will be relatively painless and hard to screw up?