Doc, I haven't a clue as to the makeup of the HEI, all I know is, it is the ONLY OEM inductance type module that actually extends dwell time to make more spark, and when coil'd right, are downright indestructible. It is better than the TCBI systyems of the PerTronix and Unilite and other drop in systems by far, as they have NO drivers for dwell extension.
As far as the pickup, no-one I am aware of has a two piece easy change pickup setup, just the full circle ones. I don't use the stock HEI pickups or reluctor/armatures.
joe, It isn't the first time I have seen it, as I posted above. It is VERY common for the coil to layer short and take the module out from overworking the resistance to it in the trigger wire circuits. I see it all the time in coil in cap HEI's, and it is more common than the large cap gurus would have a person believe.
I would also think that if the mechanical advance was sluggish, so is the shaft to reluctor movement, which requires the dist to be completely disassembled and cleaned, then regreased. It would be the stiffened dead grease holding the shaft ftrom turning free inside the reluctor. HEI's have the tendency to NEVER get looked at until they are darned near dead. So the greases emulsify, lock up the mechanical advance, and make the thing the real nightmare it really is.
I'd also be very careful with replacing the weights and center for that dist. I'd suggest the weights marked 41, center marked 375. These parts are common to late 70's/early 80's Chevy Suburban with 350 engines, EVERY new crate engine and the entire ZZ crate carburetted engine family, small and big block.
Do you have these numbers on the weights and center?? If so, I'd keep 'em and use a Crane adjustable vacuum advance, p/n 99600-1. This kit has a vacuum advance degrees stop plate that needs to be mounted differently than the Crane instructions to work correctly, not hard to do. And, it comes with three sets of mechanical advance springs.
The Crane kit and the correct number weights and center will make that dist come alive, if you want it to work right. I have a series of 6 pics that can help, give me a regular e/mail address that I can send pix to, and I will do so, and help you through it. I do it all the time for everyone.