I run a 416 in my duster, same block has yours, eddies heads ported,1 3/4 super comps, 630 lift solid roller cam, ported victor intake, 850 double pumper, 14-1 comp, made 582 hp, and 544 lbs torque, heads holding back, will need better heads to get 700hp, (i hand ground my lifter area) (i did not know anything about the water issues back then (5years ago) i guess i got lucky, One problem i had was i lost the frost plug behind the drivers motor mount, so i went to chevy 400 small block deep lip ones (they are the same size), outside of that i had very good luck, just make sure you install oil passage frost plug by the oil pump passage area (mine was not in the block when i bought it) and welcome to the site,