If I remeber right, knee knocker trucks came with an additional weatherstrip around the actual door. Some squarebody trucks had them too and you can still buy the seal for those.
https://www.soffseal.com/ss-9352 I wonder, have any of you guys tried adding this additonal seal to the doors of a '64-'66 truck? It seems to me that even with the top quality press on seals installed cabside, these trucks still could still benefit from the additional door edge seal with regard to both water intrusion and wind noise. Also, I suspect that air conditioned trucks traveling at freeway speeds in hot climates would likely gain a modest improvement in the cooling efficiency simply due to less hot air intrusion. Has anybody ever tried it?