I just did that. No problem, the end of the cable is square and fits into the socket in the speedometer. Then just tighten up the knurled ring that holds it to the back of the speedo.

There are four 10-32 (I think) nuts that hold the speedometer head onto the studs in the back of the dash. The bottom nut nearest the drivers door is a bugger to tighten down.

Another little piece of advice here. If you need to replace the defroster hoses, do it before putting the speedometer in. The hole in the dash where the speedometer normally is offers good access for your one hand while forcing the hose onto the duct.

fredstev
(Fred Stevens)
1951 Chevy 3100 series pickup
http://webpages.charter.net/fredstev/Lurch.jpg