Power Steering Gear Swapout

[wxman1]

Have a 69 SWB Fleetside w/350 CID and TH350 Tranny.
Current power steering gearbox is leaking from the bottom
seal. Soooo...went to the local salvage yard and got a replacement (supposedly from a 69) and started the swapout.
Everything is hunky-dory until I take the steering shaft coupler
off the old one and put it on the new one. Well...the splined
shaft on the old one (the one I removed) is almost 1/4 inch
bigger than the one from the yard. Hmmmm. This salvage guy is usually very reliable and knows his parts backwards and forwards. The other possibility...and more likely...is that the previous owner used some later year parts on this truck. I checked the casting numbers. There are large numbers and small numbers. The large casting numbers match (between the two) but the smaller numbers are different. Soooo...should I just take the old one back and see if he knows what year it is...or is there some way I can tell by looking at it. Confused.

Jim M.