I have been stuck in this project because I decided to proactively replace the water pump since I had the front of the engine mostly apart.
Perkins had TWO versions of the 4.154. One they made and one that Mazda made under license. My engine number is A07_J13352U. The J means Japan and that means Mazda.
A good engine was made by Mazda I was told. But it is NOT the usual North American version with North American Accessories. The manual posted earlier in this link has the INCORRECT water pump part number listed as U5NW0053 (hand written) corrected to U5MW0053 (still not correct for a Japan engine). The good part number is 136315100A (Mazda) I have seen this NA version manual, with the hand written pump number, posted all over the web
I removed the entire water pump casting and took my manuals (also North American) to the Perkins dealer. One of them spotted the J in the engine number and said, "you have the Mazda version!"
A day later I had the perfect drop in pump unit !!
(learned more about Perkins than I wanted to, but now I know I have the Japanese version.)
Now on the the alternator project...