1970 Duster factory chassis paint details.

This may help you. I've relied on it for years here in my powder coating shop.

Mopar Chassis Color Chart

Legend:
BC: Body Color
GB: Gloss Black
SB: Semi-gloss Black
CI: Cast Iron Gray
N: Natural Steel or Aluminum
MP: Manganese Phosphate
CC: Color Code

(*): Some Mopar core supports are body color with semi-gloss black sprayed
on the grill side. There are some variables from what is shown above.
Assembly:
Front Unibody subframe assembly BC
Inner Fenders BC
Firewall BC
Core Support BC*

Transmission Components:
Transmission N/CC
Driveshaft N/CC
Transmission and driveshaft Yoke N/CC
Differential Housing SB
Clutch Linkage N

Brake Components:
Brake Drums SB/N
Disk Brake Shields N
Calipers CI
Master Cylinder GB or CI

Axle/Suspension Components:
Axles N/CC
Third Member SB
Upper Control Arm GB
Lower control Arm GB
Inner and Outer Tie Rods N/CC
Tie Rod Adjustment Sleeve SB
Center Link MP/CC
Idler Arm/Bracket CI/CC
Suspension Components(con’t) Strut Rods CI/CC
Torsion Bars GB/CI/CC
Shocks SB/CC
Rear End U-Bolts N/CC
Rear Leaf Springs N/SB/CC
Backing Plates GB
Spindles CI/CC
Anti-Sway Bars N/CC

Steering Components:
Pitman Arm CI/CC
Steering Box N/CC

Exhaust Systems:
Muffler Hangers and Clamps N
Exhaust System and Mufflers N

Gas Tank Components:
Gas Tank N
Gas Tank Straps N/GB
Gas and Brake Lines N