Early A vs 73 Duster, parts swap help

PS is supposed to work with the Doug's D450 Headers - I'm banking on it!

Summit application table says "yes" with PS: https://www.summitracing.com/parts/dou-d450/applications

This link says it doesn't work with the 727 transmission: Dougs Headers D450 1963-1966 Dart Barracuda Valiant A& LA Ceramic Coated Headers

(and Yikes! They cost even more than when I bought mine)