This reply is a bit late but it's the first time I've ventured to these parts of the forums
Anyway, if you're still monitoring...
Telstars are a great car (my old man has an AR TX5 which I have driven lots over the years). Don't take the 'give up' option ;) I'd start by pulling the head off - you say _suspected_ cracked head - maybe you'll find it's only a gasket - they are a very reliable motor and I can't imagine 'em cracking heads under any normal circumstances. If it's gasket it's a cheap and easy fix. If it is a head, get a head reco'd or maybe just from a wreckers etc. and fit it. I doubt it'd have any other serious problems for you to find - my Dad's AR still runs nice and compression test shows all cylinders still withing factory spec after 320,000+ kms and even being run overheated once or twice etc!
AFAIK there is no difference in the engine bay between TX5 and GL - just different bodies - but I'm not sure how different things were in AS compared to AR. Should be no probs though - get a Gregorys manual and make sure.
Oh - why do you suspect cracked head anyway and what tests etc. have you done to confirm?
If you have some basic tools and mechanical knowledge (or mates with such assets - then all you need is beer!
) then get a Gregorys manual and do it yourself - they are easy motors to work on. I'd be happy to help with more advice etc. but I'll wait to hear from you first.
Steve.