Have you replaced the thermostat? On my 92' B250 I had to remove the Alternator and I think the A/C compressor. to properly remove and clean the housing. Also just recently I had to replace the radiator cap.
A Dodge B250 Van does not have a mass airflow sensor.
I have a 1989 Dodge B250...it has overdrive
No.
Center of the firewall.
Yes
Yes.
Under the hood on firewall in center, above engine.
It is inside the distributor.
voltage regulator is part of the engine computer
Black box under the hood by the battery
No, Dodge does not use inertia/reset swithces.
On my 92 B250, the voltage regulator is integrated right into the alternator. The engine computer is the voltage regulator on a 1989 Dodge Ram Van.