Any new information on reproduction manifold for my ‘74 Dodge dartsport 360.

Some longer-period cams work best with longtubes. Two-bbl cams don't care.
Hi-overlap cams don't come alive unless they do have longtubes
The factory 340 cam is kindof on the fence. It has 44* of overlap. With the AVS carb, headers only make a little more power, but with the TQ, she comes alive.
I have never heard of a 360 that lost power after the longtubes went on, and the tune was in..
Just trying to help.