magnum swap questions
IF it's carb'd, why dick with the tone ring and all that? Just run a small block distributor and MSD and be done with it. I'd only sweat the tone ring if you're going FI and need crank position sensing.
Also, why not run the full serpentine belt setup? Without the A/C or power steering, it's as compact as the LA stuff, and way more reliable. Automatic tensioner? Heck yes. The Magnum alternator hooks up identically to an A-body alternator, so similar mods would work, but the factory regulator circuit is so simple, I wouldn't be afraid of it.