FWIW I've badged MSD as Must Soon Die. The race grade products are worth owning and there are systems built in the '70s and '80s that are still working fine today. But the consumer grade products are completely hit or miss, and when they're a miss they're a big miss. I've been left stranded in 3 of my own cars due to failures in an MSD ignition system over the years and I've diagnosed issues ranging from misfiring cylinders to poor quality REF signals to misinterpreted timing signals and random stalling back to consumer grade boxes.

Large cap HEI in stock form will spark across a .100" plug gap with plenty of energy. Stock DIS systems in good shape can easily throw spark across .500" gaps. Unless you're running in an RPM range where the stock ignition system is having trouble or you have a specific set of conditions that are causing the stock system to perform insufficiently, I personally see no need to spend extra money on an MSD. If anything I'd get an improved aftermarket module and adjust the computer controlled dwell period in the stock calibration for slightly longer spark.

More sparks in a given time frame can definitely cause more frequent parts failure. LT1 owners are probably familiar with GM's Optispark vent campaign in the early cars. Ozone created when sparks occur plus moisture in the cap would react and create nitric acid which would quickly degrade the rotor, cap, and even the distributor itself. The positive ventilation installed in the Opti ensured no buildup of ozone or nitric acid. I've used that same thinking plenty of times on standard distributors. Small cap HEI distributor rotors often get "stuck" to the shaft due to rust and I've seen the insides of the distributor full of corrosion from the terminals in the cap while the end of the rotor just sort of dissolves. In my '57 I cut the end off an old carburetor dashpot with a .020" orifice and installed it in the small cap dizzy. I connected the other end to ported vacuum so air would only draw through when the throttle is open. That was in '93. I have never changed the cap or rotor and they are still in great shape today. In our 5.7 Vortec vans we have problems with moisture buildup in the cap after a large rainstorm or on days with high relative humidity and large temperature swings. It's so bad it can actually cause a no start. In the 20 or so repeat offenders that I've installed positive ventilation the moisture problems are completely gone, and we've moved from changing the cap/rotor at 40-60k mile increments to changing it at 100k mile increments (or when the dang plastic body fails). When using a multiple spark or high voltage spark ignition in a street distributor I would definitely consider a similar modification. The more sparks occur, the more ozone is present, and the greater the potential for acid formation.


Wasn't there an LT1 manifold swap somewhere in this thread?? :)
EDIT: EagleMark Thread Split