Do original lock cylinders fit repro handles?

[Rust-O-Matic]

I got a new pair of reproduction exterior door handles off ebay for my '66 earlier this week. One comes with a non-locking button for the passenger side, the driver side handle comes empty with no button or lock. They are goodmark brand, and appear to be what all the major vendors sell.

All was well until I tried to put my original lock/button back in the new handle. The lock seems to fit in there fine, but the retainer pieces that hold the spring in do not. The opening in the handle is too tight, and feels like I'm going to break it. After doing a little reading on here and on other vendors' sites, I noticed that some new lock listings say they only work with aftermarket handles. However I do not see anything that says aftermarket handles only work with new locks.

Does anybody that's already been through this have any input? I've contacted the seller, who says the originals should fit, but I'm not sure that's true. I just need to know if there's something wrong with my particular handles or if I just need to order the "correct" locks (which are almost twice the price of the handles).