I don't think that particular radiator has enough capacity for the 340 high compression engine it only has 2 rows and 22" wide maybe if it had 3 rows (just a guess on my part).
I'm not sure why the Chrysler engineers decided that the 340 & 426 come standard with 26" radiator
I try not to second guess the engineering they only had all the cooling capacity numbers and testing to determine what will work.