I also forgot to mention that sometimes the power valve can hit on the boss that sticks up into the cutout on the main body where the bolt from the base plate bolts on. Does that make sense?
The best way to check for interference is to take the gasket off the metering block and with the power valve in the main block stick it on to the main body and make sure the metering block doesn't rock on the main body.
If it does you can grind that boss away until you get clearance.
Don't know why I forgot that until now but I is very common.
