Incandescent to LED rear lights

I hate to throw a wet blanket, but this what you have done is not a safety upgrade at all -- it's a downgrade. To make a safe, good-performing LED lamp for an older vehicle application is not an impossible task by any means, but it is not a simple or trivial one, and "LED bulbs" like the ones you installed don't (ever) result in a lamp that gives adequate safety performance. Not even when measured according to the standards that were in place in 1971. There are critical safety performance issues involved with a car's brake/tail/turn lights; they need to work in specific ways to do their job effectively and keep you safe on the road. Just looking at a homemade or aftermarket brake light and saying "Yup, looks nice and bright" isn't good enough. Before anyone spends money or time on this, see here and here and (more technical stuff) here. See also here and here.

The '71-'73 Dart brake/tail lights are not very strong performers in stock form, but there are various ways of (genuinely) improving them substantially. It has been done, and I understand Spaghetti Engineering has (or will soon have) a good LED conversion for this application. Simple basic maintenance (see here) including cleanup and assuring proper ground will go a long way. Better bulbs are readily available. My own upgrade on a '71 is described here — although US regulations still permit rear turn signals to be red, the US DOT's latest research shows you're up to 28% less likely to be struck from behind if they're amber, and UMTRI research shows following drivers react faster and more accurately to your brake lights if your rear signals are amber rather than red.