At this stage wait for Guy to reply or take out the old one and look for part numbers mate problem with a clipper esp 1990 you dont know if they used old new parts or upto date parts? Either way if its out you can keep housing and change internals or just take it direct to VAG for an exact match?
I had issues on my 89 where the cross over caused me issues in parts plus mine had a TSR short block with PAS yes on a 89!
The only other thing I know is some water pumps can be adapted to fit, but with different pipes
BUT BEWARE SOMETIMES THE RUBBER PIPES COST MORE THAN THE PUMP! Hence I suggested you make sure you have correct water outlets and pulley sizes.
Not much more I can offer you unless you take it out mate?

Look like this one?
