I'm very pleased, overall. As with all things Cougar under the dash, it was a bit of a struggle, but no more so than if I were replacing filament bulbs. I can now see my instruments with ease.
On the downside, I can't dim my dash lights using the headlight switch. Even my add-on AutoMeter voltmeter and temperature gauges (not mounted in the dash) no longer dim.
You should be able to dim. Post this at classiccougarcommunity.com and the community can walk you through diagnosing it.