If it is while you are braking, the rotors or druma are warped.
Vibration , damage from sun exposure ,
Vibration, no but excessive bounce or wheel hop, yes.
Upper ball joints need replaced
It cause down shifting is making the engine roar most trucks hardly use a jake brake
vehicle is still in gear, step on clutch
most likely it is a cylinder missfire it might be a broken flywheel (cracked)
Power Steering Pump
A common cause for an automatic choke to stick in a 318 Dodge truck is a dirty carburetor. A spray can be used to clean the carburetor to stop the choke from sticking.
The first Dodge truck was built by the Dodge brothers in the 1920's.
change the fuel filter
The very first dodge truck was built about 1920
Your vibration can be from a lot of sources. Tires, balanced? Checked them for a separation/out of round. Tie rod ends, stabilizer, ball joints? Even a torn motor mount can cause a vibration. A warped rotor can cause a vibration when the high spot passes through the caliper. You have a lot of things to check out. Good luck