Engine replacement for a Westerly Discus advice

[Tranona]

Not sure if it's been suggested already but the OP could also consider a reconditioned like for like unit.

After weighing up the options when we did it, it was the cheapest & easiest route ....same exhaust, controls, loom & gearbox. The last engine lasted 30 years so no reason why the replacement shouldnt do the same.

Not a good idea with an ancient 3 cylinder Volvo. Not only are parts difficult to find and expensive making a rebuild costly but the engine is not very good in the first place - which is why it was superseded by better engines over 30 years ago. better to bite the bullet and instal a modern engine that will last 30 years during which spares if needed will be available and during that time benefit from the increased refinement, lower noise and greater charging capacity.