Jets are gettin big!

So i got a 70 duster with a ratty 360 in it
Got about 245deg of duration and 107 deg lobe seperation, 10;1, 3.55 gears, 25" tire (street car), 26" 3row raiditor, 8 blade water pump, 160 high flow thermostat, dual 12" spal fans (it sucks a pice of paper to the grill easy).... Timing is set 10deg at idle and 32deg max (im guessing around 2500rpm)
So i got a 4150 holly 750 dbl pumper, ive got it idleing on idle circuit, powervalve is dailed in, im stumped on the main jets (primarys) .... I started at stock 70, temp went to 200-210 quick, and about 14.5" of vaccum at 40mph...took her back home and swaped in sum 74s.... Temp droped around 190-200 and vaccum picked up to about 15.5".... Swapped in sum 78s and temp stayed about the same and picked up another .5" of vaccum
How much more gas is this small block gunna need??
I would like it to run 160-170 on 70deg days, so it can survive in the 90deg traffic days!!
Or is that asking for too much??