Gaz,
the way i look at your motor is it dont matter if its on a cat d or not; there are so many cossies out there that are in alot worse state than yours not on a cat D
people buy on condition (well i do anyway) i'd much rather buy a cat d with light front end than a clear car with a rotten body
dont be a goon, fix the fucker and have some fun it in; dont break it for the sake of a small repair.
matt