Ol55 -- You need to check the casting numbers and date codes on the blocks to be sure of what engines you are talking about.
But think of it this way ...
1954 and 1st Series 1955 trucks were Advance Design. In the second Series 1955, the design changed to the Task Force trucks. The TF trucks had a lower design so the radiators sit lower in relation to the block. That's why the earlier engines have higher water pump mountings, whether it be a 216, a 235 or even the first year of the 261. I have one of those 1st year 261's in my truck, btw. It was a replacement crate engine built in 1959 but came out of the 1954 mold because it was built to be installed in an Advance Design series truck. I mention this to illustrate that there is more to this than just reading the casting numbers. Thus -- 261's out of the '54 mold will have the higher water pump. 261's out of the later molds will have the lower water pump. But ... to conclude the lesson, at least in the case of the 261's, GM changed the design for the main bearings at some point between '54 (when the 261 came out) and '59 (when my engine was made. So we needed to cross check the casting number with the date code. I didn't and we had to modify the main journals to accept the earlier bearings. You can read more about this in the Tech Tip we put together about my 261 rebuild.
Rebuilding the 261Summary -- If the engine was meant for an Advance Design, Art Deco or earlier truck, it will have the higher mount for the water pump. If the engine (235 or 261) was meant for a Task Force series truck, it will have the lower water pump.
