Sorry for the long post.... I replaced my water outlet neck with one from a 12v 2nd gen and run into a few minor issues and wanted to come here and ask. The reason I swapped them is because the PO put a 91.5+ radiator with driver side outlet in the truck and there was an abortion of a radiator hose installed. I wanted to eliminate 6 hose clamps (was 8 total) and picked up a 94+ outlet which exits to the driver side. I picked up a thermostat and gasket for a 94 which fit the WO neck fine, but it doesn't completely go through the engine hoist point as the '90 gasket did. I'm thinking that the hoisting mount probably changed the 1st to 2nd gen trucks and are a tad thinner but wanted to come here and ask the pros for an answer. I installed an additional o-ring in front of the tstat to get things fitting right, but I know this isn't the way it was from the factory. So can anyone confirm/deny the setup differences between 1st and 2nd gen trucks?

 

I did a change over awhile back and the 2500 used 2 square shoulder O-rings for each side of the lift plate, as I try to remember not having that part when I needed it.

 

I've done the same thing on my crew. 90 engine, IC'd radiator, and used a 94-98 12 valve t-stat housing. One, you have to use the 94-98 t-stat, two, you have to use the 2 required t-stat gaskets/orings for the 94-98 t-stat. I don't recall any fitment issues though? I bet the second oring is the one that is supposed to fit the ID of the lift bracket? I do remember putting everything together with only one oring and it leaked. I'll try to find the part numbers for them if you need them.

 

Going off what sooty stated I'm good. I installed a square shoulder oring but I installed it between the housing and the stat which in turn pushed the thicker gasket through the lift plate. Thanks for the info guys.

 

Outer gasket 3927305. Inner seal is 3925466. FWIW, you can google image either of those part numbers to find a diagram of how it goes together .