Why not build a 340?

Main reason the 360 is favored over 340 now is cost and 20 cid. Unlike HP torque is pretty predictable most street performance engines will be around 1.2 lbs-ft per cid so that's 24 lbs-ft advantage or basically one gear size.
So the average gear for a decent 360 seems to be 3.55 which would mean a 340 would need 3.73 gears. Not the biggest deal in the world.