All my early Q bolts (63 - early ‘64) measure at 1-5/8’’ from top of head to end of threads.
The smooth shoulder measures 3/4‘’ from top of head to start of thread.
There were two styles of fonts on the Q, most of the ’63 models had the small Q. Then late ‘63 and into the first months of ‘64 they used the large Q on these long bolts used with the non-crimp struts.
My H3 came with the small Q and my L3 came with the larger Q, which was used for the rest of the Stingray Series to ‘73.