Yes, I have some experience, although I'm currently running a four barrel on my 250.
The engine is a .040 over 250 with 250 head. Cam is Tom's Thrifty cam with 1.84/1.6 valves and roller rocker arms. I bought a factory rebuilt Holley 0-80457SA 600 cfm carb. The engine started immediately when I went to break it in. I ran well as a matter of fact until the secondaries opened. I tried the two stiffest springs I could find, metering block with bigger jets than the fixed metering plate that cam in the carb, but nothing worked. It would fall flat on its face on the top end. I talked to Tom a couple times but we couldn't figure out the problem.
Eventually my engine guy said to return it to a 4 barrel so I took the plug out and removed the epoxy. As I was putting it all back together I found that the screen on the fuel inlet fitting was full of what looked like paint chips. I have no idea how I could have put them there since there are two see-through filters on the fuel line. The only thing I can think of is they were in there from the Holley rebuild, but I will never know for sure because I didn't check it before installing it.
From the time I did have the 3 barrel running I will say it had good throttle response and ran cleanly up to the mid range. That being said, the 600 runs really well too...gas mileage be damned.
