383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

IMO 75 Hp was a good guestimate, but prob less.
Both tuned in; that is flat AFR through the top, jetted for max power and torque, etc.
Disconnecting the secondaries on a '750', my 340 lost 25 - 30 hp, and the peak dropped from 5500 to 5250. The difference should be higher than that but ran out of time to tune in the secondaries. So that's a real life, but imperfect example of halving carb size.