Not sure if this helps but here is a picture of my 50 with everything stock. I have a set of newer 4x4 rims on there to roll around on. The rims were on it when I got it (from my dad) so I am not sure what they came off of but they seem to work decent for now. By the look of them and the fact they went on sometime in the 90's would make me guess they are pre 89' like bigbadswingdaddy suggested.
Maybe you will see a set that looks like this.

http://i901.photobucket.com/albums/ac218/Root2812/1950%20Chevy/untitled.jpg


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1950 Chevrolet 3100 5 window
Original 216ci and SM420 4-speed