I wouldn't buy a timing light just yet. Most likely dealing with high resistance in the starting circuit, whether it be cables, connections or the starter itself. Sounds like you are on the right track.
The crane unit is indeed an externally mounted electronic ignition. I believe they use the stock rotor.
Tandem Axle Wheel & Tire Package $629
4 Matte Black T08 14x6 wheels, 4 ST205/75R14 Kenda Loadstar tires
Single Axle Wheel & Tire Package $379
2 Matte Black T08 14x6 wheels, 2 ST215/75R14 Kenda Loadstar tires
MOUNT, BALANCE & FREE SHIPPING INCLUDED IN BOTH PACKAGES
CARB REBUILDING - FAST TURN-AROUND. $100 +PARTS
LED lights, Hubs, Spare Tire Carriers, Chrome & Powder Coated Lug Nuts - Red, Blue & Black
PM or email me firstname.lastname@example.org