Which GZ pump did you buy?
The pump may or may not be able to pull the vacuum you want, that depends on how good you have your motor sealed up on the rings and seals and gaskets and how tight you can get the drive belt, been there learned that
Good luck, do NOT put the vacuum fittings in the fuel pump block off plate You will fill the puke tank in one or two runs
My motors ended up liking the fitting in the top of the cast aluminum valve covers with no breather caps on them, I ended up buying some of the cast polished aluminum valve covers from either Speedmaster or Pro Form from Summit Racing that had no holes in them and drill them with a large Unibit bit to fit the rubber grommets I needed when I was using a PCV only and ended up buying another pair and bought a screw on two piece fitting that I could use a AN hose from the pump to that fitting only and did not put any other holes in them, I would disconnect that fitting when I would change oil and use a small funnel to pour the oil into the motor through that fitting
I didn't mount my pump on my front motor plate so I could tighten it or loosen it up Never again The most vacuum I could pull was right at 5.5 inches no matter what I did other than remounting the pump better, that was with the GZ enhanced pump, their best one
I have bought two Moroso vacuum pumps since then, one three vane and one four vane, I'm hoping they both work better, I'll really focus on sealing the motors better and mounting the pumps so they can be adjusted to tighten the belts really tight
Good luck on your deal