[atoman]

Good morning! Thanks in no small part to your guidance, I recently completed an engine rebuild and transmission swap on my 3.8L 2006 Grand Caravan SXT. My problem now is that it won't start.

• Red dot on dash illuminates with key on
• Key fobs are black

All OE FOBiKs are black, all have Immob chips, and your "red dot" is telling you the system thinks you don't have a valid key (and is probably in "lockout" mode - more than 3 consecutive attempts to start without valid, paired key thus no crank)
This could be a problem with antenna, module (SKIM) or key - does keyless entry activate power locks with buttons?, have you tried the second key?

 

[atoman]

Yes, there can be trouble brewing if correct cam & crank parts are not put on the motor (compatibility issues with SBEC vs NGC PCM)

However, even if the crank signal was absent (unplugged sensor) it would not prevent the engine from cranking over...