Dave....these guys are correct.....

Old style 850 Holley are 1.560 Venturi X 1.750 Butterfly
Holley List #80496 950 1.375 Venturi X 1.750 Butterfly

On our 950 Stage 5 we keep the venturi at the stock 1.375
and on our Stage 5 950 Plus carb we open the venturi up to 1.400 by opening up the customers HP body or we also will use the Proform "850" body which already has the venturi at 1.400..

Hope this helps...Jesse