Like oddball said, your wondering whether a carb twin 40' inlet manifold for a 1600 nova will fit the head of your 1600 SV engine?
Well if my memories right from noticing it on mine comparing the gsi head to the sv head they should match up.
But just browsing the DT catalogue there are slightly different part numbers for the manifolds they list, so i would be a bit cautious and try and look at the manifold before you purchase it.
Assuming the standard power is around the 75+BHP mark, i would say an increase of about 15-25% so possibly near 100BHP.
I think i read on Tom S site somewhere about estimating BHP increases with various induction methods, maybe able to give you a better indication.
Although mines an SV block the head is actually a Nova GTE/GSI one. Which has the better inlets etc.. for more oomph.