I have been wanting to install door lock knobs for ages. I bought originals that dry rotted and tore off leaving just the threaded Barrel and this was about 12 yrs ago. Recently I ordered the anti theft cal custom style knobs because they were listed as 35 Chevy knobs. To my dismay they were a #10 thread. Mine was a #6 or 8. I kept them because they were too inexpensive to send back. I have been thinking about some sort of insert into the knob that might match the thread Of the door lock. So today I was at Ace hardware and I was looking for the seat bolts I need and I see screw anchors left on the counter. It hit me like a ton of bricks. Why couldn’t I stuff that in the door locks I have and let the anchor self tap into the rod. I gave it a shot and it worked.
Ran into the same thing Mario on my '39. The newer style door locks fell over the threaded shank on my doors. I wrapped the threads with teflon pipe tape and screwed them on, and they seem to be holding well so far.