It much easier to cut them off and replace them, and they usually aren’t worth saving.
Torque the manifold bolts carefully IN THE PROPER SEQUENCE and re-torque them with the engine hot.
Mopar A engine intake manifolds are notorious for leaking near the exhaust crossover when improperly torqued.
Pase real life cam
The factory manual has information that you can’t find anywhere else. Most of them are simply factory manuals condensed for the home mechanic.
If you have to use aftermarket manuals, get several of them from different publishers as each may have something that the others missed.
You will need a universal joint if you are installing the relatively tall 1983-& later 318 “police car” manifold.
Clean out the exhaust crossover/EGR passages on any used manifold before you install it (hot-tanking is best).
A 160 degree thermostat will not make up for a clogged radiator and a 195 degree thermostat will not fix a poor heater.
Also make sure that you put the thermostat in the right way (point up, spring down!
Summit Racing offers some really neat carburetor inlet fittings with replaceable fuel filters built right into them for many carburetor models Make sure you have the right temperature range thermostat: Your engine will not run right without a thermostat.
The temperature range you select will depend upon climate, intended use, and engine modifications.
Don’t use manifold gaskets that block the exhaust crossover passage in a street motor.
This causes severe driveability problems, especially in cold weather, and the choke won’t work. Also, plan on replacing all of water and the vacuum hoses.
I recommend removing all parts from the top of the engine (Carburetor, coil, wiring harness, distributor) so you can get to the manifold bolts.