Got one of the Mopar performance electronic kits in a 440. Kit 8 years old, (yup have had to replace the control box a few times). Parked car about a month ago, running fine, no skips etc. Tried to start this morning, no spark. (This determined by holding a spare plug against the neg batt. terminal with #1 wire hooked to it, spinning motor over. Changed control box, no go. Checked ground to control box, (OK). Changed coil, changed to a new in box distributor, checked wiring from 5 pin connector to resistor, coil, etc, all good. With key in "run" position, have 12 volts on both sides of resistor. Using remote switch, spinning motor over still no spark using spare plug test. Anyone got any ideas? Not sure what may have happened while car was just setting. Oh yes, rotor button IS turning.

"IF YOU'RE UNDER CONTROL, YOU AIN'T GOING FAST ENOUGH."

Wriggle the wires at the bulkhead connector and try to start it. Start and run are two different circuits out of the ignition switch and sometimes the wiring at the bulkhead will get corroded. If you disconnect the wires at the starter relay on the fender you can get turn the key to the start position and use the test light to see if you get power to the positive coil post and not worry about grinding the starter over a bunch.

Nearly every time that I've had a No-Spark situation, it has come down to a loose connection somewhere. A loose ground, a wobbly crimp connector, something like that.

What Stump said pull the yellow wire off of the starter relay to disable the starter then have someone hold the key to start & at that point (1) the coil positive primary terminal and (2) the wire at the "point" of the ECU pentastar need fire (use a test light or VOM). If no fire at both what Franken said work back toward the bulkhead for the open. You mentioned the MP "kit" so I'm assuming this is a 4 pin ECU. If a 5 pin then 2 terminals on the pentastar connector need fire in "start". The ECU you've replaced it wouldn't happen to be orange in color would it . EDIT Check the reluctor gap in the new dist which ain't the original cause of the no start but is commonly misadjusted

Check the reluctor gap clearance..
Should be 0.008 using a brass feeler gauge, if too wide the box won't fire..

Just my $0.02...

Define..."Too wide".
Mine had slipped to .020 and the car started and ran fine until I leaned on it, then it spit, sputtered and popped. This was unfortunate, because I learned this while trying to drag race in front of plenty of people! What a pisser, too. Back at home doing the Mopar CSI, I determined the wide gap was the cause of the misfiring. Once corrected, all was well again.

Another possibility is that the magnetic pickup in the distributor is actually bad itself.... had that happen to me once. It also could be a bad cap, rotor, or the coil-to-cap ignition wire is burnt/broken or one of the ends pulled off.