I run a stock OHV490 / 17HP TEC. in the ARMA MOD XR class...The emulsion tube and jet of choice is, as suggested, "blue tube / brown .040 jet"
MOD XR is a governed class @ 3650 rpm, a factory stock engine with jetting, velocity stack / aircleaners and custom header pipes.
E.C. does have a nice velocity stack / air cleaner adapter for these carbs. However if your running the stock governer and/or throttle linkage, you may need to lathe 15-17 degrees taper/angle off the intake where it mounts to the head...this will allow enough clearance for your filter to fit well and not bind up or rub against your linkages.
How far and fast you want to go, you may want to open the brown jet a little, and the brass one in the bottom of the bowl, depending how your header likes it
Don't forget there's spring with the jet AND the emulsion tube, and they do sell a screw to replace that solenoid. Also worth noting is how bad the Ethonol is eating up the O-rings....These are great carbs, but can be tempermental.