The two things that scare me about the Cossie engine is
Trying to find one that has not been abused, If it's cheap, probably a good reason why
The cost of engine components . When you find that the bargain you found is a pup. Expect to pay £200+ for a head gasket set
That's before you buy any parts to put the problems right !!??
That said, I would not say no to a mint Cossie engine