Jandro remove those plastic ties asap.As the radiator heats up it will melt them,regardless of car speed.What about the stock 69 firebird retainer plate.It should work with slight modification(ex. 90 degree 1/8 stock welded/bolted to lip of plate,brace top of radiator,mark holes on top core support and drill for 3 small self tapping screw).This just an idea from the pic.Others with similar f-bodies may have a better.By the way,SWEEEET
looking car and engine.
Roger.