Much easier to tailor an advance curve on the MSD distributor than on an HEI plus the HEI is a space eater. (and ugly)BillyG,
Thanks for the kind comments. I agree with many of your statements, & yes, if you fitted a MSD 6AL or equivalent 'box' to a car that had points ign, you will very likely notice improvements such as easier starting, idle quality etc.
My point [ pardon the pun ] was & is: that if the engine had HEI & it was replaced with an MSD box, there would be NO difference in all but the highest output engines.........except for a lighter wallet. Also, the 'box' ign systems add more components & connection points that can fail, so there is also a reliability factor involved.
Now, some of the elec ign conversion kits that retain the stock coil & ballast resistor/resistance wire really just provide breakerless triggering, but no increase in spark energy like the HEI does. So replacing one of these with the MSD 6XX might well provide an improvement you can feel. But overall, the HEI is hard to beat for cost, reliability & performance.