I looked at RA for the thermostat housing info and found the Gates #34702 you talked about but no Gated #33910. Why not use GM parts? Anyway, it boils down to which pump you have because there has been an updated water pump thrown in the mix. One of the GM applications asks if the GM pump on the rig is a casting #12562459 and then that tells you what housing to order and why. Gates does not share that. If the pump has already been replaced with an aftermarket pump, then the casting number will not be there or if is a GM pump will be the casting number I speak of or another casting number.
Thank you for taking the time to research into that for me.
RA is actually the place I'm going to order from and I too noticed they listed 34702, but not 33910. I actually got 33910 from a post on this forum, the guy purchased the exact pump I'm getting and he got 33910 to mate to it. I had to search RA by product # instead of by vehicle to find it, but they do have it on there.
The reason for gates vs GM. I'm 9/10 the type of guy that goes Acdelco even if it's more expensive because I've had horrible luck with aftermarket stuff, however after reading several posts on here and other forums as well, it seems the gates water pump is highly regarded and there is a pretty substantial price difference so I took that into consideration and decided to go away from Acdelco this time. Since I'm going with a gates pump I figured for the sake of fitment, it's probably best to go with the same brand for the thermo housing.
I actually contacted Gates themselves and the guy I spoke with was just as confused as me so it wasn't much help unfortunately. However we muddled through it and he ultimately came to the conclusion that 33910 is for "OE and most aftermarket pumps" and the 34702 is for a specific "updated GM pump" so he said 33910 is the one I needed to get. Albeit he didn't sound very sure lol.