Looking online, apparently Stanley was a division of Dayton. The current Stanley Spring company does not make automotive leaf springs, as far as I can tell.
From 2020:
DaytonStanley (299 x 198).jpg
via the Wayback Machine. Gone today.
Maybe Dayton now? If you look at RockAuto, they sell both the Dayton and the Dorman springs for the GW. These have the same part numbers and weight rating, though the price is significantly cheaper for Dorman. No offering for the rears, only for the fronts. 5 leaf 960# 97372 $203 vs $137. 6 leaf 1045# 97380 $198 vs $123. 7 leaf 1335# 97400 $203 vs $92.
If you search the part numbers for the springs you are interested in, ie "97380 leaf spring" you will find several places offering these springs. Kinda suspect these all come from Dayton somehow and the manufacture and sourcing of them has been somewhat fluid in the recovery from the pandemic. Maybe the Daytons are the same spec as the Dormans but a switch from domestic to overseas production? Unlikely the sellers will tell you if they know. Dorman is like Crown or BJ's, a distributor of a collection of parts they either curate or commission.
Shipping will be expensive with these springs. If I wanted Dorman, I would ask my local friendly auto parts store if they can get them. Parts stores can get Dorman stuff very easily, usually. Possible they could be handled by their regular deliveries from the local warehouses, and save you some money on shipping. Ask if they will match the RockAuto prices.
Also, I'd probably go with Crown for the rears if that's all that's available. True it's likely Chinese origin but Crown is pretty good about monitoring the quality of what they sell, even if it's not the best. Crown sells through distributors (largest is Quadratec), unless you live in Massachusetts and can buy direct from their warehouse. If you have a problem with their products, you can call the warehouse and talk to someone in the USA.
You could go direct to the domestic custom manufacturers like Deaver or Alcan. This would assure you get exactly what you want, expert consultation on the sale, and best quality - at a premium price. Supposedly the BJ's lift kits come from Deaver.
You really want Monroes? IMO the regular production KYBs would be a much better choice, and the upscale KYBs (or better yet, Bilsteins) if you can afford it.
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