I looked through some old dyno sheets I had.

I did some SB RPM heads for a guy about 15 years ago.
He was having some troubles getting the car to run what it "should" with the ported heads and new cam.
He fought with it one season, the car didn't seem to respond to anything. He was looking for solid 10's and it was stuck in the 11-teens.

The motor had never been dynoed........ so I told him, before you spend more $$$$ on the motor, pull it out and get it dynoed.
The combo he had "should" have made 575hp, and if it did, the car should be solidly in the 10's.
He couldn't seem to find anyone in his area that was set up to test Mopars, so he ended up shipping it to me.
He sent his headers, carb, timing light, etc.

I put it on the dyno, warmed it up, set the timing where he said he was running it......... and on the first pull it made 576hp.
The reason the car wouldn't run the number was not a problem with the motor.

He had sent a new carb to tune, and after playing with that a bit it ended up making 587hp.

He swapped out a few suspect parts in the car, got a new converter, had the trans done.......and iirc, it was running 10.60's first time out the next season.

Anyway, that was 2003 when I tested it(heads were done in 2001 or 2002).
280cfm RPM heads, 419ci, Victor intake, 1050 carb, 1-7/8x3.5 headers, 264/268-108 roller, 1.5 rockers......... 544tq @4900, 587hp @6400.