They can use the same pump if the rotation direction is the same. Dependent upon blower, governor location, and engine rotation on the engines determines either right, or left rotation. There are standard variants, and high flow for higher horse applications.
These are two gear pumps just like an oil pump in an engine. There is a sliding shuttle valve that is spring loaded to relieve excess pressure in the system when the pump is supplying more fuel than the engine is burning. In reality when the valve operates, this temporarily disallows vacuum, or suction on the line through the primary filter till the excess pressure decays and the spring loaded shuttle valve slides back over a port allowing the pump to draw again. This is done by uncovering the port that bleeds pump discharge into the pump suction side. The shuttle valve, and bore this valve slides in wear over time. In my case, the plunger valve, pressure relieving spring, and stroke limit pin are all worn in, and out.
This is the shuttle:
This is the relief spring:
The stroke limit pin had the spring coils worn into it. The shuttle and it's bore has grooves worn into them. Can't really tell by the low resolution of the posted photos but they are pronounced.
Nowadays, new a/m pumps for those are about $150 and rebuild kits are just over about $120. Reman originals are just a bit more $$$ but probably worth it as the shuttle valve bores are sleeved back to original size after machining back round. I've never used an a/m pump in this application so really no input there.
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