Horse power drop using early A 273 manifolds

IDK about a log to log comparison, but I can offer this;
I had a 73 Swinger with a stock long-block low-compression 318, with a 4bbl,a 2800TC, and 3.23s. Oh, and the factory single exhaust. At the time, it was a lotta fun.
Fast forward a decade or two.
I dragged that smogger-teen out from under the bench one day (Swinger long gone to Mopar heaven), resealed it and dropped it into my 68 Barracuda, as a winter-motor. Pound for pound those cars weigh about the same.
Well now; the Barracuda was set up with a 360/4-speed/3.55s, plus TTI headers and full-length 3" duals.
I dropped the 4-speed out and put the worked A904 in, that had been behind the teen, with it's 2800TC.
I left the TTIs and 3" duals.
And I cannot begin to tell you about the amazing transformation. Thinking it must be the 3.55s, I swapped in some 3.23s, and it was still a powerhouse. I then went to 2.76s where I finally thought the output was maybe a lil less,than what I remembered from the 3.23 Swinger. So I concluded that maybe 2.94s would be close to par.
So the point is that the TTIs and free flowing exhaust were probably worth at least one rear gear change, maybe a tad more. In this case, from 3.23s to 2.94s is ~10%
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I swapped the smogger-teen into that Barracuda, every winter 5 years running; 5 different transmissions and as many rearends, and more.
And every spring, the 367 went back in. Except one spring when the 318 was just so so much fun, I think it was June or July , yeah July long weekend, before the 367 went back in. And after that, it stayed in.
In my wildest dreams I would never have imagined that headers and free-flowing exhaust could wake up an otherwise stock smogger-teen with a 4bbl.. Oh I gotta tell you one more thing, I installed enough valvespring to rev 5500, but usually shifted it at 5200, or less.
Probably not what you were interested in, but I thought it could be useful.