JW, KN, and KR were the same, except for the two letter codes and the date codes. Techrev makes the best new replicas, and they can be stamped with JW and 1970 date codes if needed. I ordered a set for my 1970 Trans Am, because the JW wheels are too hard to find and too expensive.
http://www.tachrev.com/JWwheels.htm
I could be wrong but from what I see on their website they are NOT REPRODUCTIONS but rather they are VISUAL REPLICAS, built using USED OEM 14" centers welded into used 15" rims. You'll still need to sandblast, fill in incorrect stamping on the rims, stamp your desired marking if desired, and then paint. Finding correct factory appearing stamps for sale is not likely IMO. Just wouldn't want someone to see your post and jump on their site ordering wheels thinking they were buying reproduction wheels painted in original type finishes. Their advertising is very carefully worded and should be read slowly to be sure folks know they're buying used parts welded together that are a project that requires finishing.
These quotes are copied & pasted from their website.
"Rally II wheels are now available refinished to better than O.E.M. specifications."
"This picture is there to show you what the wheels will actually look like with accessories/correct paint on your car. "
"This wheel is a COSMETIC & DIMENSIONAL COPY of the ORIGINAL "
"Our wheels are made with ORIGINAL GM PARTS"
"Wheel nut tapers are within spec."
"Media blasting,final prep & paint are left for your attention to detail"