I had one on my beater '69 300 many years ago.

It did pick up the part throttle torque and response noticeably. The tiny runners for the primaries do work.

At WOT, I always felt the stock manifold was actually a little better, though.

This was a decade or more before I got into dynos and dragstrips so all I've got is seat of the pants info. Trying to judge by feel, that's all I've got for ya.