Transmission/speedometer problems

[TurboJim]

1989 chevy r3500 454 tbi 2wd turbo400 trans.  Well, I have a problem with my speedometer, the previous idiot owner burned up the turbo 400 that had a mechanical speedometer, and he replaced it with a turbo 400 that has a electronic speedo pickup in it, then he snapped the mechanical speedo drive off of the old trans by lifting it up by it,  So how do i hook up the mechanical speedometer up, what changes do i need to make to the trans and where can i purchase the parts? the dealer has already laughed me away, and no junkyard near me will let me buy it off the side of one of their transmissions, at least not without buying the whole thing.

[Captkaos]

it should be just a converter on the side.