I believe they might be the same as I think Westerbeke bought
Universal in the late '80s...so the Universal might be the older
engine.

You are correct that Westerbeke and Universal are the same company.
There is no reason to suspect that the Universal must be older than the
Westerbeke, either trademark can be purchased brand new today.

I suspect Westerbeke may run both lines so they can appoint more dealers in
crowded markets. Dealer "A" is the "exclusive" Westerbeke dealer, but to keep
him hustling and competitive in price they give the same product to Dealer "B"
and call it a Universal instead.