I got a rear rack for my bike, I go to put on, and I realized the eyelets don't have threads. This is probably an early 80's steel bike, of unknown brand and origin. It has 27" tires (not that I think this matters for this question).

It looks like I probably have enough clearance for a nut on the back side of the eyelets, but I won't know until I can get to the hardware store. Is there something different I should be looking for to use for this? Some kind of threaded clip or something? I bought this for a backup commuter / medium distance rider. I have it all ready to go except for the rack (and fenders, but I'm not sure I have adequate clearance in the back). I'm gonna take it to the LBS and see if they have any ideas, unless someone here has any suggestions for a tight clearance on the rear wheel?