The pipe slides up inside the blow mold and the bolt will go from the outside of the blow mold into the conduit, which is basically a stand and securing it onto the conduit. So I don't think I could get a clamp on it. I am also thinking that I should use a couple nuts to give it a little more stability.

I like these coupling nuts to go inside. 3/8" across flat so I would still need the JB weld or something... https://www.amazon.com/Pack-4-20-Coupling-Plate-NCUP004C000STLZN/dp/B07TKC86RW/ref=sr_1_4?crid=33A2PQWQEWX6D&keywords=1%2F4-20+coupling+nut&qid=1669171727&s=industrial&sprefix=1%2F4-20+coupl%2Cindustrial%2C140&sr=1-4

IDEA>>> squeeze the conduit at top??? Then put the JB in there so it wouldn't fall out?