Just wondering hen was the last year the intake manifold heat shield was used on the big blocks. The insulation that goes under the intake manifold

This topic has come up a few times in the past:

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/190879/re-440-intake-heat-shield.html

FWIW, the consensus is that they are not really a heat thing, more for sound deadening. And when you think about the fact that the heat riser is already running through the center of the intake manifold, it kind of makes sense.

And FWIW the factory called it a "valve tappet noise reduction package."

I saw a 72 service manual with a description of the pad in it, so they went at least that late. How much after that I do not know...