Here is a picture from US Army TM9-8025-1 Ordnance Field and Depot Maintenance GMC Model 302 Engine. Item A is the tube I mentioned in the previous post.
My 228 GMC (and most of the others I've seen) have a boss on the head, but it hasn't been drilled and tapped. It is near the hole where you have your temp sensor installed.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
