I have had the same problem as well on the alternator.................I would like to have gone for 240 Amps after doing some initial calculations of possible loads on my build but I am struggling to find a high output small compact unit. Therefore I had to compromise and go for a 175 Amp. The unit that I purchased is below as it will fit in the restricted space both in length and diameter:

WOSP LMA300HO - Universal Race Alternator

Just drawing up required new mounting brackets................