420a/ECC engines were found in:
--- SOHC 2.0 ---
Dodge Neon/Plymouth Neon (1995–2005)
Dodge Stratus/Plymouth Breeze (1995–2000)
--- DOHC 2.0 ---
Chrysler PT Cruiser (non-US) (ECC)
Dodge Avenger/Chrysler Sebring (1995–1999) (420A)
Dodge Neon/Plymouth Neon (1995–1999) (ECC)
Mitsubishi Eclipse/Eagle Talon (second generation, 1995–1999) (420A)
--- 2.4 DOHC --- (The 2.4 is 180deg out of phase with the 2.0)
1995–1998, 2000 Chrysler Cirrus
1995–2006 Chrysler Sebring
1995–2006 Dodge Stratus
1996-2007 Dodge Caravan
1996-2000 Plymouth Voyager
1996–2000 Plymouth Breeze
The pattern looks approximately like this poorly drawn and inaccurate diagram, that seems to be sourced from some magazine, not Chrysler docs, roughly:

And here's the poorly written article from which that diagram was extracted.
Here's a few pics of a crank out of one:


And here's a "composite log" from some MS user that appears to show the ? as being narrower than the ?:

Any more actually reliable data from the OEM or careful measurement most welcome.
Fred.