Electronic ignition for Slant 6

Ignitor I is older and requires keeping your ballast resistor. Ignitor II is more like GM's HEI (or Ford's TFI), so I would use that. I recall that Ignitor III offers multi-spark and rev limiter, but might be less reliable, plus may not even have a PN for a slant. Avoid the Crane Cams XR700. I had one on my 69 Slant and 65 383, but the control box failed on one (fortunately had a spare box in trunk) and the optical pickup failed on another, plus it is old electronics which requires keeping the ballast.

On my slant, I installed a GM 8-pin HEI & its coil, triggered by a Mopar e-distributor. I pulled parts from a 85-95 Chevy V-8 truck. TrailBeast here sells the new parts as a kit.