Re: Universal 5424 transmission
Personally I would say the logical choices are between :
Getting a rebuilt HBW 50
Getting a whole new Beta 25 as eherlily already suggested.
If this were a relatively new engine I would say you might benefit from the longer life of a brand new ZF transmission, vs. the rebuilt HBW50.
However, the reality is that the 5424 is limited in remaining life - partly by wear, but mostly by diminishing spares availability. Last time I bought a raw water pump for my 5424, it was $350 - and going up.
So extend your 5424's life in the most economic way possible, or bit the bullet and replace the whole drivetrain.
Bristol 31.1, San Francisco Bay