I have been around mopar (sixpack/and GM tripower holleys) for a long time. If I have learned anything, its that the reason most people that have them and they don't run right is years of hack jobs and so called rebuilds over the years by prior owners
1. First and foremost, if I ever see mech linkage set up on a set of OEM six/tri Holleys, I walk away: All that means to me is that an owner somewhere down the line had percieved problem with his carbs, so they changed them. Who knows what else they changed out as well.
2. Even the brand spanking new six setups you see for sale are NOT put together correctly,. The metering blocks are not correct for the 340 or the 440 setups: Yes, they will run out of the box, but not a efficient as they could be
3. The linkages on a proper vacuum operated 6 setup have a VERY specific setup. The steps to set up and adjust them are availalble. Holley back in the day was very specific if a carb or carbs were removed, EVEN if your kept all the linkage adjustments the same and didn't change them, holley stated to go thru all the linkage set up instructions again when you and reinstalled them
4. Years of wear, poor maintianence, and hack work made these setups run poor over the decades. Leaking throttle shafts, clogged metering block passageways, improper float adjustments, replacing parts with the wrong parts, etc What I mean by this is that the many parts might fit, but the part was NOT calibrated or meant for the holley 6 setups. Even holley has cross referenced the wrong parts over the years for these 6 setups
I would recommend anyone interested in these setups: Buy one from a QUALITY restorer that is willing to help the setup and tune once bought, OR. Get one of the new setups, and have a partner help set up the basic tune
Remember back in the day when these units were new they ran great: In fact the 440 six's would get the 440 hemis off the line.
As far as an AFR goes, none is really needed to get a 6 setup running, although it does help to get a spot on tune . The middlecarb does the work until the gas pedal is pressed, and vacuum opens the outboards
3. Forget calling holley about six pack tuning. They lost their tech knowledge on their 6 setups a long time ago