Of the 7 water pump mounting bolt locations, 3 of them are threaded and 4 go all the way through into the engine block. The only holes open to water are the 2 directly below the large coolant holes.

 

the long ones.....check 3rd one...my 360 had this one open too. Maybe just oil..

Photo from FABO

 

What GD is that? Never seen that particular one before. Interesting.

 

Thats a GD-318N from the old CAT catalog. Cheap and effective but N/A now. The Milodon original has the idler on the opposite side. Lots of the Speedmaster stuff looks very similar to the C.A.T. stuff and its all China produced unless otherwise stated....
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Also be careful about BOLT LENGTH. There is one "magic hole" that can go in the water jacket and break the lower end of the cylinder skirt, requiring great amounts of bad language, and money to repair.

 

Agree, the 3rd hole down on both sides especially the driver side is 3/4 inch from a cylinder wall! Measure twice, torque once.