Top 5 A-body mods...

The mini starter was the best mod.
But the things I've done that just improved the car:
Shocks! I didn't realize how bad they were until I replaced them.
Radial tires! Nothing in the world like having a bias ply tire come apart on you at 60 mph.
Paying an experienced professional to buff the paint. absolutely amazed at the difference it made.
Oh yeah, an FM converter hidden in my glove box. Hidden so my grand daughter doesn't mess with it. :)