Edelbrck vs Trick Flow

On my stock 906 headed 383, going from 1-3/4 x 3 headers, to 1-7/8 x 3 headers was a gain of 13hp, peak vs peak, but there were points in the curve where the difference was about 20hp.
That’s a 25ci smaller engine with heads that flowed over 50cfm less than a 408 with TF heads.

I haven’t tested too many SBM strokers, but the best ones used bigger headers.

1-5/8” headers on a 550hp+ type build seems like a mismatch to me.
My friends Pontiac Stocker runs 1-3/4>1-7/8 step x 3 headers.
Those were bought to work on a 400” combo.
A couple of years ago he built a 350 to try.
He thought maybe some 1-5/8” would be a better match for the smaller motor (that uses smaller heads, that have smaller valves, and it got a smaller cam).
The 1-5/8” headers were down about 15hp.

As for the Ede vs TF thing....... if the TF’s are no better than mildly reworked RPM heads........ that’s really fine.
Since....... unless you’re doing your own porting...... the TF’s will be less $$$ than reworked RPM’s.