Differential oil for a 7/1/4” sure grip

NO SYNTHETIC! My friend had a one man hotrod rearend shop. Only used torco dino oil. Would NOT warrantee his work if the customer insisted on synthetic gear oil!
Ok thanks for letting me know about the synthetic, I will check the u joints when I jack up the car here before too long, I think I’m going to send the carb over to woodrift and let them do their thing to it, just a little concerned when she’s driving alone, so far she’s been doing great she loves her car