If you ask for that at O'#### or similar, they will want an application and their books don't go back that far. So pick a u-joint for a Chev 3/4 ton from however far back their books/computer go. That should be a #1350. Next size up is #1420. That won't fit. Take the dimensions with you to check.
A better solution would be to go to a driveline specialty shop and ask for a #1350 u-joint. There's one near where I live. They don't ask you year, make, model, engine, paint color, etc. They just get you what you need. They carry quality (Spicer) parts at better prices than your generic parts store.
