Help me identify my spindle

So I bought drum brake spindles off someone on ebay so I could upgrade my 9" to 10" spindles, and use the SSBC brake kit. The add was for spindles for 10 or 11" brakes, 1967-72 Duster, etc. I go to put the kit on today and put the new spindles on, and everything looks the same. The nut fits on it, the spindle looks the same, and I can put 1/2" bolts through the bottom two holes (I thought you had to upgrade to 10" spindle to even use 1/2" bolts with the lower ball joint). My drum was a 9" drum, so I'm pretty sure the spindle I took off would have been a 9" spindle. What is the difference here? How can I tell which is which? Did the guy on ebay rip me off, or have I been running a 10" spindle with my 9" drum and 9" drum bearings? The funny thing is, the SSBC brake kit, w-153, the spindle nut is WAY too big for either of my spindles, and never mind that they forgot to send me the calipers, pads, or the bolts. Man I'm getting sick of things like this. Help! I can measure something with digital calipers if I need to.