340 heads on 360?

The factory wouldn’t waste the time, effort and cost doing this if there wasn’t something there.

stock head with 1.88 valve - 185 cfm range, 2.02 valve - 215 cfm range. But if you fully port that stock head with the 2.02 valve you could get it flow in 280 cfm range so you could take advantage of a larger camshaft with more lift and better springs allowing more fuel and air to enter the combustion chamber.