Bit of an update, the original engine went back in, still has a small oil leak somewhere, otherwise runs good. Got some nos parts out of the states to fix up the alternator connections, in the process of putting a set of blades on it and fixing up the blade brake. Gave it all a clean and the whole driveline is really tidy!
Finally found a much better trailer today, the rusty one was a write off, this one will need a couple repairs but nothing too serious.