I have a sleeved brake booster body listed on eBay. I had it done before Sierra retired and I no longer have a coupe. Check the listing and if someone on here wants it, send me an email OFF Group and I will cancel the listing as long as there's no bids. It's $250 with no core exchange.
https://www.ebay.com/itm/223546438076
Also if you haven't done so please check out my website with shopping cart. Don't be scared by shipping prices, I usually give huge refunds on shipping. Also postage prices listed are USA only.
https://600miles.com/
Parts - Service & Free Advice Since 1981
Miles - z600miles@...