I'd um (As usual) on the engine oil. I flushed both my Dodges engines through throughly and now run them on 20/50, by preference Halford's own. I've never had any problems with it. Though Gearbox and diffs I use recommended straight oils.
Try Rye oil, they are knowledgable, and friendly http://ryeoil.co.uk/ryeoilstore/
Modern lubricants are designed for high speed small tolerance engines, hence you can now get hundreds of horses out of a little engine. Our old work horses were designed to run on poor fuel and irregular quality lubricants, they are a lot more resilent than modern kit.