points to electronic 1966 dartgt

Electronic distributors have 2 wires for the pickup, w/ a double-bullet connector. Search ebay for photos.

Changing to electronic ignition should not require a new harness. Simplest is to use a GM HEI 8-pin module & coil. Many posts on that. Cheap at junkyard (85-95 GM V-8 truck) or buy new parts from TrailBeast here (~$150). Could also buy a new distributor w/ HEI module for $45 (ebay).

If you do need a new engine harness (for other reasons), there are 3 in 1966 - engine, lights, & wiper. The engine harness depends on the engine type - slant, SB, or BB/RB. Year One or M&H (their source) and not cheap.