All the ones listed above are pretty reputable from what I have been reading for the past couple years.
Ones that have not been mentioned I know of are Tenny and Vital Power Inc.
Although I have not had experience with Tenny I have seen evidence to support him as a good HO builder but I have seen just as much, if not more proving his alts either don't perform well/at all or will cause fires and fried electrical systems.
Vital Power Inc is a seasoned company(started in 1999) but I have only ever seen one. From the looks of it, it looked generally stock but the fellow who owned it claimed it to be rated at 200A @ 2k rpm but he said he clamped it just over 225A @ 2k rpm. If the dude was full of ish or if the company is full of ish I really don't know.
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