Thanks for the replies, it's most encouraging indeed.
To answer a couple of questions, photos, I'll get a few posted up when I get on the pc to compress the files.
Nick, the thoughts around the 2500 transplant are;
The 2500 was in my kit car and is known to be in good order, effectively its also free which is another bonus.
The original 2000 I'd like to have kept but now having been able to run it for more than 2 minutes due to various problems I can hear a rumble suspiciously similar to mains bearing woes. Also when warm the oil pressure drops off from 40 psi cold idle to less than 5 psi hot, only rising to a little over 10 psi hot at 3k revs. Then there is a muted whirring chirping noise which I'm attributing to worn cam bearings. This is all theoretical interpretation at present.
Oil pressure relief valve checked, cleaned and washers added just in case it was stuck open, curiously this has a lot of wear to the sides indicating its been quite active in its past!?!?
A large part of the 2500 decision lies with the finances, which are slim.
Shame really as the 2000 has +20 domed pistons with good bores.
It's a weird old car combining a mixture of really good quality modifications and work with some dreadfully attended bodges.
Almost as if it was someone's pride and joy once with some nice upgrades attended but was then subsequently ravaged by a max power reader.....