WATER PUMP DIFFERENCES:
250 impeller vanes have a small surface area but makes up for the lack of surface area by increasing the amount of vanes. This old design reminds me of the ones I replaced in all the trucks and cars I have worked on.
Fast forward onto the next generation--the 300. The 300 has a larger surface area per vane and increases it's impelling efficiency by giving it a curve as well as maximizing its space inside the water pump body.
Swapping the 300 pump onto the 250 will not work as the shaft on the pump is shorter and will not connect with the oil pump. In order to make it work, you would have to weld an extension onto the 250 oil pump shaft or machine a longer oil pump shaft.
250 left, 300 right:
250 pump uses a sealed bearing and the 300 is an open bearing design:
So Vaney.....:
