Thanks for all the information and words of wisdom, chaps. I can see your points. Your suugestion of taking some measurements and comparing the Richards one is a very good one. They are not a million miles from me and besides, I would be going to fetch the chassis myself which would make a check more convenient.
I can see that once I get into it, one would no doubt be upgrading replacing etc. whatever needs doing in order to get a viable 90 at the end of it all. Would it be worth it monetarily? Maybe not, but like most have said. It would be the devil I know.