does exhaust help in this motor build??

Dive stock lowerend, stock e7 heads, 514 / 524 lift cam , duration at 50 -218/226 ..stock intake,.
after the headers would it make more power if it had say 40 in of exhaust pipe on each side vs. open headers???

There is going to be an optimal length somewhere between the collector and the end of the pipe.

I would say testing will be needed.

Take to track, then take a spray of paint and pant them then make a blast down the track
and where the paint burns off is where you cut the pipe. it'll be a strip around the pipe where it burns.
Close enough for for county work.