Water Pump Technical Question

[rn2fine]

Have a 72 Burb with 350. Bought block new from GM last year. Has Vortec heads and Vortec manifold. Put GM serpentine system on when recently assembled. Serpentine system including water pump based on 90-92 F-body. I wanted to put a water pump on the block that is compatible with the coolant recirculation outlet on the Vortec manifold. The problem I have is when I went to mount a Vortec compatible water pump onto the block it did not cover a third hole below the water pump bolts on the passenger side of the block (water just came gushing out). There is a third hole there that the previous pump covered, but the new pump does not. Does anyone know if there is a solution for this that would allow me to mount the new pump and cover the hole so coolant does not leak out. Hole is not threaded. Maybe a plate of some type?