Intake upgrade?

I have a similar 367 build, now with an Airgap, and am quite happy.
The problem I ran into, was that with 3.55s, a 292/108 Mopar cam, and a Single-plain intake, it was nearly impossible to drive slow enough to parade the car, cuz the engine was not happy running there.
Eventually, I found a 3.09 low gearset, a smaller cam, and the Airgap combination would go down to 3.66mph@500rpm@5* timing. After that, it pulled itself along quite nicely.
When that cam lost lobes, I bought/installed the next bigger cam from the same manufacturer, and this cam does not like 500rpm. But it does pretty good at 550=4mph, still at 5*.
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With the 3.09 low and 3.55s, my equivalent starter-gear is 4.12s, to your 4.56s.
For you, 6550 is ~60 in Second, 82 in Third.
For me, 6550 is ~ 61 in first-over, and 77 in Second, and is 99 in Second over, cuz I have a GVod/splitter, lol .
On the street, I just gotta say, that the opportunity to run Second gear to redline are few and far between. I was very happy with my former cam, 223/230/110, and was very sad when it died. The next cam, 230/237/110 was a bit of a bugger to warm up to, and for a long time I was not a happy guy. Eventually, I got it tuned pretty good. but the truth is that I have been waiting ever since, (2005) for a good excuse to rip it out.