I don't know about Airflo, but my Frink undertailgate spreader needs something like 14 GPM to run both auger and spinner at the higher delivery rates. Lots of dump hoist pumps max out at 8-10 GPM and they have to be would up to make that. Some of the systems with the pump in the tank are either 4 or 8 GPM and limited to 1,000 RPM.
My personal choice is the belt drive pumps with electric clutch. Those make 20 GPM at 2,000 RPM (round numbers) and handle a spreader easily. My current central system uses a power beyond valve for hoist and plow. When you engage the hoist valve the spreader stops temporarily. If I was going to do it again I'd put a flow divider in ahead of the valve body and send constant flow to the spreader. That way the excess flow runs the hoist and the spreader speed is constant, regardless of pump output. But that means 3 more hoses inside the cab, which I wanted to avoid. If I put the flow divider outside the cab it would get all messed up from salt splash.
Current system has the clutch pump, 20 gallon tank, total system capacity is near 25 gallons. Valve bank is under the body with cables from the control handles in the cab. I had to run lines into the cab, for the spreader control, but I mounted the control on pedestal on 5" exhaust pipe and left the hole in the floor open where the lines come up inside the pedestal. At least now if I get a leak it will be contained inside the pedestal and drain back out rather than soaking the interior with oil.
