Phil - it might be simpler to buy the brackets from ERA. I'm not sure but original style brackets might put the alternator into the suspension uprights. The alternator needs to tuck in very close to the engine as seen in this picture, to provide clearance to everything.
I don't think it's very expensive - consisting of two metal bar bracket on the lower side, the adjusting bar for the top and a long bolt and spacers. It doesn't use a cast-type metal lower bracket like most OEM.