Here's what I think (for what its worth)
First the easy one: On the wires, I haven't used dielectric grease. Never have in many many vehicles. The rubber boot is usually ok, and if the leads and cap are new, it seals up just fine. Since its high tension (lots o volts) I wonder if that goo is a good idea.
Occasional backfire - kinda need to know more. Does it do it on shut down? Cold? On Deceleration? Randomly? When its wet out? Is the timing and dwell set right?
Backfire can be caused by carb mixture or shorting of plug wires. If its random, its harder to diagnose. If the dist cap and wires are bad, best replace them anyway and then see if the backfire problem changes.
