I'd look at the basics from the Service Manual (short version)
Kickdown band adjustment loosen jamb nut, run in adjuster then back out 2 1/2 turns.
Linkage adjustment... With choke disconnected or held open have someone hold the kickdown lever on the tranny all the way forward (or make tool with spring to hold). Loosen kickdown lever adjustment bolt, holding the lever back, adjust the slotted bar forward till is in contact with the carb. stud.