Bad solder joints on the instrument cluster circuit board can cause stalling and odd electrical behavior:
http://youtu.be/9OwrhVOHe1Y
Possible causes of fault code 54 (cam sensor signal) include the wiring, connections and grounds, the crank sensor (which has already been replaced), the PCM itself (5 or 8 volt regulated sensor supplies dropping out) and (worst case) a possibly cracked flexplate (flywheel).
I doubt that it's a relay, although power interruption can occur in the PDC (underhood fuse/relay) box. Its close proximity to the battery means that battery acid can corrode connections in the area.
As asemt stated, the PCM will dump any fault codes if it loses battery (memory) back-up. This can be battery terminals, wiring or the PCM itself. Remove and clean the battery terminals to start and follow the circuit to the fuse/relay box (PDC) and out to the PCM.
You might want to get a service manual and powertrain diagnostic procedures book for a guide to repairs:
http://www.faxonautoliterature.com/1997-Caravan-Town-Country-Voyager-Van-Repair-Shop-Manual-Original-P15908.aspx
http://www.auto-repair-manuals.com/Chrysler-Dodge-Plymouth-1997-Town-Country-Caravan-%20Voyager-2.4L-3.0L-3.3L-3.8L-SFI-CNG-Powertrain-Diagnostic-Procedures.html
A scan tool/data recorder is useful for 'live' information that may occur at stall, but leaves no clues behind. A scope view of the cam and crank sensor signals at stall can also be useful. A cracked flexplate will cause them to lose sync.
The Chrysler dealer has a Co-pilot (data recorder) that can record everything that the PCM sees up to the moment of stall. This can take a lot of the guesswork out of the repair and start a proper diagnosis.
Stop replacing parts! Always diagnose first. Always use OEM parts, used is OK as long as they are proven good. Review the repair history and interview the technician if you can to get an idea of where things were left and then put together a plan. You may want to start at the beginning again to diagnose this properly.