My Dooley uses a passenger car pick up (and it is a Mellings), pulling the pan is worth the effort IMO, It was always my understanding that the Dooley pans use an OEM blank, but could very well be bad info, The 10 quart Mercruiser pan I have is over an inch deeper and no way it will fit in a jet boat...
More than 3/8" of clearance and there is the possibility of sucking air under a hard run, always between 1/4"-3/8" clearance.
I welded the pickup to the pump and welded two tabs on the bottom of the pick up at 1/4" from the surface of the screen (that way I can check for contact with the pan during a teardown

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It's almost a life death situation for the engine if this does not get done right...IMO..
GT