I don’t know. I was 15 in 1967 and wasn’t paying attention.
Your questions feel pretty “gotcha.”
I am NOT playing “gotcha”. I’m offering a potentially educational conversation.
The answer is “no”. The B-17 was retired almost immediately after WWII; the B-36 was retired in 1959. S, “no”; neither was involved in weather modification (or anything else) during the Viet Nam war.
The B-17 contrails over Germany were highly detrimental ... even potentially lethal.
To the crews of those aircraft.
Have you any idea why that might be the case?