The oil gauge was electric like the 69 Chevelles and used the same sender. The harnesses were stand alone units that assembled along side of the dash harness and plugged into the bulkhead connector at the firewall. You could get them in any fleet car as far as I know (cop car, firechief, or taxi), but was not available to the general public. They could be had in both 120 and 140MPH versions. I have owned both. They generally sell in the 1800-2500 dollar range. The last one I sold I got 2200 for but it included a new harness to make everything work.