If you measure the old ones at the knurled diameter and the new ones at the same place I would expect to see the old ones be a bit smaller, even if they are the exact same studs from the same batch / lot.
The process of installing and removing them in a tight fitting hole should have squished the knurling down perhaps 8 or 12 thousandths on the diameter.
Just so you don't think you have the wrong thing if they are at all different, as they should be a tad different from new to used.
I had a similar problem on a 65 f350 We had a long time ago. I was driving up the interstate when 5 of the 6 studs holding the left rear wheels on sheared off. I got it stopped and then on a trailer without the wheels falling off. I found what were supposed to be the right studs, but could not get them to fit. Being in a pinch, and needing to get the truck back on the road, I ground some of the knurled portion down so I could at least drive them in with a big hammer. If they are just to tight I see no problem with turning them down a few thouthandths so they will press in. Just don't go so far that they won't lock in the hub and stay stationary when you tighten the lug nuts.
Grigg
