missing speedo on 1993 f250 4x4 diesel w/1988 rear end
 

Howdy y'all,
I just bought myself a 1993 f250 non-turbo idi diesel 4x4 w/ 5 speed stick. When I bought it the man who owned it said the speedo didn't work as the rear end was changed from the original limited slip to a 1988 posi-trac rear end. He said the original speed sensor was on the rear end an' I needed to buy an adapter to make the speed sensor work with this rear end. Well, I took his word for it, but I'm not sure he knew what he was talkin' about as I could find no place for a speed sensor to fit. I really don't want to change the rear end to a newer one as I'm short on cash from buyin' the truck. Is there any place else I can hook the speed sensor or a different type of sensor I can buy to go on the tranny or someplace else easily without any major work? I'm pretty sure I can't hook up any type of sensor to the rear end to get my speed, but did the 5 speed tanny retain the port and gears that drove the pre '92 trucks speedo's? if so can I hook up to that with the correct sensor? I saw a sensor on an auto parts website listed for '93 that said was labeled as Vehicle speed sensor for transmission. Is that what I need? and i so where is the port on the tranny located?
I'd appreciate any advice on this matter.

Thanks,

Hondo