Poor idle and off-idle performance after distributor swap

Sorry if this has been asked but;
have you tried the old distributor, with the previous amp, to isolate the problem to the new system? Then transfer the pertronix into the old distributor to isolate the problem to it?

IDK anything about the Pertronix. Is it polarity sensitive, like the Mopar magnetic pick-ups are? If it has a magnetic pick up, it will be polarity sensitive. And when the pick-up polarity is reversed, it will fire just fine at idle. But as soon as the Rs begin to rise, the timing will go erratic, and the light will see random flashes and missed sparks. Mine was impossible to drive like that. It happened to me that the Mopar pick up died on the hiway. I subbed in a spare set the idle timing and began to motor away. But the engine ran like crap. Then I noticed that the wire colors were different from the one I removed. I happened to have a polarity reversing adapter in my tool kit, so I subbed it in, reset the idle timing, and this time the car motored away as usual. After I got home, I swapped in a Pick-up with correctly colored wires and all was well.
Later I found out that the pick-up I had initially installed, was not for an SBM
Like I said; IDK anything about Pertronix.
Jus trying to help.

This points directly to two things;
1) your throttles are not in the right place up on the transfers slots, and
2) your float-level may be high or unstable.

That 262 XE cam is likely about [email protected], am I close. As far as cams go, this is pretty small, but the right idea for an 8/1 nominal Scr 360. I should make gobs and gobs of low-rpm torque.

From your description above;
1) your mixture screws are out too far ..... because
2) your transfer fuel is insufficient ...... because
3) your throttle is too far closed, because .....
4) your timing is too advanced..

So;
You need to set the Transfer-slot exposure, underneath the throttle plate to a tiny bit taller than wide, make it just perceptible. You do this with carb removed, the choke and fast-idle disengaged, the throttle closed, and use the curb-idle screw. Make sure the secondaries are closed up tight but not sticking. Ok flip her right side up, and set the mixture-screws to 2.25 turns out. or about in the center of their working range. From this point on DO NOT ADJUST THE CURB IDLE SCREW.

more coming

That problem is long gone, carb is tuned to perfection. Just the timing issue now.