I have had several different sets of 440-1 upgraded to the 2.250 intake valves, the first motor was a 4.375 stroke with a 4.380 bore 440 block build, it made 845 HP on race gas with a single 440-3 intake and a 1050 4500 Holley dominator carb. That was with a set of headers that the exhaust flanges weren't big enough for those heads (the motor would miss from 5200 RPM up to when we quit pulling it at 7500 RPM) but they where the only headers available that day, two inch pipes with thhee and half inch collectors
I'm sure there was another 10 to 30 HP with the proper size pipes and flanges
I'm having a 400 block machined right now for another set of the 440-1 with the 2.250 intake valves, that block is 4.380 also with a 4.300 stroke crankshaft and better rockers
If it makes 800 + HP I'll be happy