Nope, no need for the factory plate. But make sure you use the correct gasket (if you use one) when putting the water pump block off plate on, use the gasket that goes between the factory plate and the timing cover. Not the gasket that goes between the WP and the factory plate. 

 I think I'm right about the gaskets , maybe someone else can confirm.  I do remember that one of them seals all the way around the water passages (correct) and the other one is just the outer edge (wrong). 

No plate like Proppy said but I do recommend you pack silicone around the open casting where the dip stick tube passes thru  Tom

Ray a significant portion of BBFs have a DS tube that passes thru the Timing cover just behind the water pump mounting machined surface, some (Vans I belive) are "minus this" when the tube passes thru the aluminum casting it passes in an area that we always seal for security's sake

Look between the upper two cover bolts on the right of the motor (left in the pic ) ..

Here's a better pic of what Toms talking about, you can see the dipstick tube as it passes through the timing cover (just above the water passage), a water leak there can give you milkshake oil. But if yours dosnt have the tube there dont wory about it. 

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Damn proppy, you were on that like a polyester suit 
Tom I think you're dead on on the Econoline motors dipstick delio, learn somp'n every damn day...


GT