What Carb for Poly Stroker

66 Sat,
I would encourage you to run the 625 AVS2. It has annular boosters in the primaries, which brings you to a new world in throttle response. This carb has smaller pri bores than your 600 Holley [ 1 7/16" v 1 9/16" ] for better response & mileage, with bigger secondaries when you want the power.
Chrys cars used Carter 4bbl AFB & AVS designs during the glory years, including on the Hemi.
I don't have any more direct comparisons as shown earlier, but in Roger Huntington's American Supercar book, 9 supercars are listed. These are NOT magazine tests, these are his own, unbiased testing. Quickest was the 68 Plym which ran 14.6....with a 750 Carter AVS on a 440. RH estimated the actual hp at 330. 3.23 axle. A 69 Ford Torino, 428 engine, Holley 735 carb, ran 14.9 with a more helpful 3.50 axle. All the others ran in the 15s.
He says this of the 340, AVS powered [ p. 132 ] : '' One of the swetest engines of the era was the 340...'It combined power & quick response with good fuel economy.' A 'Cuda with a lowly 3.23 axle ran 14.8 @ 96 mph....big block territory for a stock engine.

I do not know how long you have been in Oz, but various Aussie muscle cars were compared & the results published in Top Aussie Supercars. The 340 Charger, AVS equipped, v the 351 Falcon GT with 830cfm Holley. The Charger was 150 lb lighter, but down 11 cu in.
" We managed to 15.5s in the Charger, while the Falcon was battling to break 16 secs. Our test crew felt that the Fal lost a lot of time below 40 mph [ throttle response? ] - an area where the Charger is pretty fast."

" The 340 is definitely smoother at high revs & it doesn't haver the 351's tendency to lose tune after hard use"