Water Pump 2.5 NA, But With Viscous... ?

Just about to order a replacement water pump for my '85 2.5 NA. It's had an engine swap to an ex military 2.5 NA unit at some stage and has a plastic fan mounted to a viscous coupling.

The standard, non-viscous P/N is: STC 637... just wondering if it's the P/N: STC 635 that I need? The engine is 100% a non-turbo unit.

Thanks for any advice.

Correct, stc635 has a threaded end on it to take the viscous unit. The pulley is different as well. Just done mine, I bought a Bearmach 'lrd workshop approved' one from lr direct for £29 and so far all good. It came with the gasket.

Thanks Huddy... spot-on. I'll get that ordered and fitted ASAP.

Alarm bells started ringing when my local LR specialist stated that early 2.5 NA's came with steel fans and a non-viscous set-up - mine has a plastic fan that freely spins!

Cheers for the guidance.