Wideband idle tuning with large cams

What's your initial and total timing? Are you running vacuum advance?

This is what I was told once, and it has work amazingly every time I've tuned a motor. With the vacuum advance disconnected, if you have it. Hook up a vacuum gauge below the throttle blades.
1.) Slowly advance the timing while turning down the idle to your normal idle 850 rpm ?
2. ) Once you reach peak vacuum at idle and it will not increase any more, you have found your initial timing point.
3.) Do the math and adjust your distributor so it can only mechanically advance to your "all in" timing. With a Mopar that should be somewhere around 34 to 36 total.
4.) If you have vacuum advance, hook it to a port below the throttle valves and turn down your idle to normal. Either change the pod to get the minimum vacuum advance available, weld the stop and file it back to the right shape, but so that it only adds 5 to 10 degrees of timing, leaving you at 39 to 44 total ting on cruising on the highway (this is conservative timing for highway cruising). Usually, you can end up right around 50 to 53 degrees with full vacuum on the freeway without gas knock. It MUST be hooked up to manifold vacuum, so when you crack the throttle open, the vacuum will almost instantly drop back to your mechanical only setting of 34 to 36 total.

This all assumes you didn't build a motor with too high of compression for pump gas and/or you are not building too much dynamic compression with your cam choice.

BTW, My wideband won't even read my idle mixture on my 493" sixpack motor until it is above about 1800 rpm, so you are lucky.