FAST55 - According to my search of the '36 GMC Parts book, it's described only as GM# 458543 "Screw, inside door locking lever". No dimensions given and the number doesn't show up in any cross-references I could find.
The '36 Chevy's used originally GM# 3654596 - Screw, front door inside lock lever. Again no initial dimensions given for that number. A later Parts History Index shows that GM# 3654596 was listed to "mix with 119010.
A search of GM# 119010 list the common hardware dimensions as: "No. 6-32 x 3/8, fillister hd., 1/4 dia. N. P.
Just IMHO, but I think that you are correct in the thread hole should be 6-32. Hope this help.
