The -1 are listed as 780 vs 750 for the rest but that just holleys rating not actual flow bench numbers. It very well could flow more but its my guess that he's doing some type of restricted class racing there are probably head restrictions which make the 780 vs 750 choice a drop in a bucket. Sure if I had a -1 I'd want to use it just for the ease of tuning alone. The -1's also had secondary p[ower valve. I think I might have an old -1 laying around in piles of parts but it would take some work.
If I had a 3310- whatever in good shape I'd throw a coversion kit on it to put replacable jets in the secondarys and go.