I got my steering box from FirmFeel, and since I wanted the larger sector shaft of the 73 and up box, I neded to send a different core. The guys at Firmfeel gave me the number for Wildcat auto wrecking which is just down the road from Firmfeel. Those guys sold me a nice box to use as a core and sent it directly to FF for just over $100. Then a couple weeks later, I got my Stage 3 steering box. It is still sitting on my workbench waiting for the car to come out of storage, but now there will be no downtime from turnaround.
As far as the blackening kit is concerned, I have used it for years on my NCRS type Corvette restoration work. I don't use their oil based sealant after, instead I use their clear sealant which holds up much better than the oil based sealer that I got with the kit. I still have to admit that it is still not terribly durable, and when I do work for a driver car that will go through puddles, I use a "fake Phosphate" paint on the blackened and sealed part.