Have had the original springs re-arched 2x over the years and are really sagging now. Mild 383, auto, occasional street action. What do you guys like? Thanks.

You can buy reproduction HD springs from a bunch of places. That would seem like a good choice for a street car. If you're talking race car then that is a whole different kettle of fish.

I'd assume you'd want the heavy duty factory style rear leaf for what you're doing...

Eaton Detroit Spring has them for around $700 plus shipping (made in USA). Took about a week and a half to get them.

ESPO Springs n Things has them for $270 plus shipping, but about a 4-5 week lead time (made in Mexico). I was more impressed with ESPO's customer service on the phone but wanted to get my car back together a bit quicker. If you search around, I don't think you'll find a complaint about them.

ESPO/Springs & Things - I've used their springs on a couple cars with great results and they've held up.
I generally go with the factory XHD spec, + 1" in case they settle some, but haven't seen much settling.
On a wagon with big tires, + 2" may be better because of all their tail weight.
You can swap in the factory numbered leaf if that matters in your application.

My buddy has ESPO on his 74 Challenger, just installed this year. No complaints, decent ride, excellent customer service.

I have Calvert monos on my 70 Challenger, installed last year. No complaints, slightly firmer ride, good customer service. I like the ability to swap rear spring segments.