It's all in the carb tune, assuming the engine is tuned correctly. You could put a 1000 cfm carb with the correct tune on that engine and it would run fine. The OP just needs to learn how to tune it.
Run fine? I guess if you have a very loose definition of fine.
I ran an Edelbrock Perfomer 600 and 750 on the 360 in my Diplomat as a test. That was my daily driver, go to work (75 miles each way) car. With the smaller carb I had about 5 mpg more economy (mid 20's) and better throttle response.
With the 750 I had higher top speed, I could exceed the certified 125mph speedo's ability to measure whereas the 600 wouldn't go much past 110.
The more you exceed the engine's requirements the slushier the carb becomes. I suspect if I tried to run a 1000cfm carb no tuner in the world, including you, would have made it run fine and the only way it could be made to even get close to the smaller carb's effectiveness would beif it was a spreadbore with the secondaries so restrained as to essentially limit it's total airflow to something similar to that smaller carb's flow. IOW, it would never flow 1000cfm in use.
Did the 750 work? Yep, did it work fine? Nope. At any street speed the smaller carb was better in all respects.
