All the essential parts for MKII Spits and GT6s are readily available, with few exceptions. A number of vendors have them.
I always used SpitBits, owned by a Brit who really knows these cars. Other reliable vendors are TSI Imported Automotive, The Roadster Factory, British Parts Northwest, Victoria British. There is a wealth of parts available from UK-based vendors, too, but shipping costs are usually prohibitive.
In general, you can purchase all essential parts new, on today's market. The rest may be had on venues such as EBay.
It's always a good idea to join your local Triumph or LBC Club, an excellent source of help and info.
And of course, ask here!! If we can't help you, you're probably beyond help!
Cheers, good luck. /ubbthreads/images/graemlins/yesnod.gif