According to the 4th digit of the VIN (C), your truck has a 330 2V M/D FT engine.

1970/72 330 2V M/D; 330 2V H/D; 361 & 391 FT engines:

4) 379521-S7-8 .. Stud-Exhaust Manifold to Cylinder Head ~ 3/8" -16 -16 x 3 21/64" long.

Two studs for the right manifold, two studs for the left manifold.

All the rest are: 20522-S8 .. 3/8" -16 x 2" Hex Head Bolts ~ Exhaust Manifold to Cylinder Head.

FoMoCo did not install exhaust manifold gasket-to-cylinder-head on these engines, just metal heat shields. Sooner or later, the manifolds begin to warp, start ticking.

Whiz down to the autoparts store, buy FT exhaust manifold gaskets and have the manifolds resurfaced.