Small Block & Big Block Chevy Specific - plastic mpfi bbc intake, anyone know what this is from? injector size?

I picked this up at my local speed shop. Its for rectangle port big block chevy. It also will accept a LT1/TPI type thortttle body, and has place for GM map sensor to bolt ot side of it. These use a GM TBI-700 side feed type fuel injector with 6 small holes in the botttom.

Other then that I don't have a clue what this came from. I'm sure it was marine.