Top 5 A-body mods...

First five steps,?...
Fresh chassis,OEM style..
Upgraded drive line...( transmission, clutch, rear end)
disc brake ,front brakes,OEM style....
Subframe connectors, welded in..
Patience,in building a strong base,to build on.. Horsepower means diddly squat(& you look like a buffoon..other wise),unless you have a plan...

No, not the first five steps, your top 5. Stuff thats out of the normal. It's pretty well established the proper steps of building a solid, safe, reliable, punchy A-body.
I'm talking about the things that every time you get in the car, you think, "so glad I did that".
Could be a stereo for some, recovering some tired seats, or mounting the same style dash compass you had in highschool, etc. The hydraulic hood/trunk lifts is a perfect example

on my '72 Valiant, she had 9" drums...so upgrading to BBP and discs was a no brainer. Can't worry about going, if you are worrying about stopping!
That said, I replaced the windshield washer system with a complete NOS system I bought local, right after I installed a fresh windshield. I used to get a big grin every time I mashed that foot pump and had a nice spray of Rain-X on a crystal clear windshield. Beaded water so well that I rarely, if ever, used the wipers. That was in Tacoma too. Another one was replacing the glove box liner, just so I could store the re-pop owners manual, and the mint ORIGINAL glove box trash bag I found under the back seat..
Replacing the front female portion of the seatbelts after driving for a year with a broke drivers belt you had to shake to get it engaged was pretty satisfying as well..

Sometimes it's those little things