My old school 340 upgrades and results.

crackedback said
Not near enough gear for a 340 with that size tire.

As you mentioned, a 28 or 29" tire will make a difference in how the car leaves.

X2 I ended up with 27 inch MT drag radials and a 456 rear gear, what's your trap rpm? I had a 26 inch tire and 410 rear, used to trap at 5800, new set up should be 6200-6500 through the traps.