There is enough demand. I have seen no less 100 forum thread starts looking for that fitting when I was searching for a work around. In every GM group from the GMT400s to the S10 to the Astro van guys. Even in one of my Van groups on FB a guy was looking for the correct fitting recently. If it existed it would sell and sell very well. Literally millions of GM vehicles used it. Problem is people like ICT Billet use the leverage for someone to buy an actual oil cooler kit.
is this new, i havent seen this yet, although not sure what 3/4-18 uns is
Oil Cooler Adapters - Adapts Engine or Transmission Coolers to Oil Line Fittings - M20-1.5 Male O-Ring
Oil Cooler Adapters - Adapts Engine or Transmission Coolers to Oil Line Fittings - M20-1.5 Male O-Ring. Part Number: RW8044
www.superiorcooling.co
if that wont work, have you reached out to non automotive fitting manufactures. titan fittings makes custom fittings