Who is the go to for rebuild? seems like a lot of "conversions" available that I'm not really interested in. Would like to have my original rebuilt vs exchange. Thanks in advance  

You might reach out to these guys: https://www.powerbrakebooster.com/

I have not used them, but I do recall seeing S30s on their Facebook feed.

If you are on FB, here's a photo from an early 240Z booster they worked on: https://www.facebook.com/BoosterDewey/photos/a.1575990385761591/4967042226656373/

I had mine rebuilt through rockauto. You send it off to Cardone in TX. It only took a couple weeks for me and it works great now. It came back in primer grey, so I painted it before installing. https://www.rockauto.com/en/moreinfo.php?pk=258880&cc=1209158&pt=1884&jsn=834

I don't know if he'll get the original back using RockAuto/Cardone.

Power Brake Booster does a fantastic job and will have it powder coated for an extra charge. Good people.

I'll give PBB a call, thanks SteveJ and Yarb!