[LH Lead-Foot]

Sorry if I am not familiar with what distributor is on a 1979 truck...it is HEI with carb?
The most common mistake made with HEI distributors is two items;
#1 leaving the old rubber insulator in the cap or coil bottom, then bolting it on. This breaks the center post.
#2 The coil is grounded thru a stamped metal strap, placed under the coil and exits in the connector housing. This is where the module connector plugs in and goes to housing ground inside.
#3 Thumbs up on the painted bolt, clamp or block where the distributor drops in.
#4 Remove connectors, cap, rotor and carefully un-plug the pick-up trigger coils two wire connector. Insert the proper terminals and plug into a DMM with it set to ohms.... Now, using a pair of needle nose pliers, wiggle each wire without moving the connector. Note that reading should not move. The wire can break inside the soft silicone covering and cause no input to ignition module. It should measure between 500 to 1500 ohms, depending on model and temperature.
Best of luck.