I don't believe a 425 LBFT 383 would lose to a 340 A body "every time". Get the Road Runner with a four speed and 4.10 gears and I just bet with two good drivers the 340 would have a hard time. Let me say it again. 425 LBFT. Nuff said.
Ain't Sure if the Super Track Pak was around for the 383, but if I'm right, it was for the 69 1/2 440 6 Paks, 4:10 Dana and SS Springs. Kinda off topic, my Bad, as Usual!