Has anyone used Amsoil synthetic Transmission lube 75W-90 GL-4 in their 1969 4 speed?

My owners manual in my '72 Duster lists ATF. It gets to triple digits in the summer here and run the ATF. However, running gear oil or motor oil in an 833 won't hurt it at all and my intention was not to talk people into dumping their gear oil and running ATF instead. I was just pointing out that ATF per the owners manual is the recommended lube.

Chuck
Ah. I was looking in my '69 Plymouth service manual.