'88 90 auto to 5-speed swap info needed...

[OorQue@aol.com]

Well, it looks like nobody wants to sell a diff without the tranny and as I'm 
not anxious to drop another $1200 for a complete tranny in unknown condition, 
I'm considering swapping in a 5-speed tranny from '85 4k instead.  Since it 
will be coming from my racecar project, I assume I have all the parts and the 
only difficulty I see is how to adapt a cable-drive speedo setup (as was used 
on the 4k) with the 90's electric speedo ... has anyone done this before or 
will I be in uncharted waters here?

(Had I not sold my 80/90 Bentley manual on eBay a few months ago -- at the 
time, I never thought I'd ever own an 90 and was more than happy to part with 
it! -- I could answer my own question but I'm not having much look trying to 
extrapolate the answer from the various other Bentleys I still have.  Live 
and learn...)

Thanks!

JG