No your ammeter will not blow up. If you're concerned about it, bypass it and put in a voltmeter.
I've seen special alternator brackets for 235s for sale on ebay, but I'm sure that other outfits sell the same thing. I usually just modify the generator bracket with some all-thread and washers to shore it up.
Yes, a Delco 10SI (63 amp) or 12SI (96 amp) is what you want. I don't recommend going into a place like Kragen or GhettoZone and asking for those models though... you'll get the bleary-eyed apathetic teenage response, "What year?"
Ask for an alternator out of a 1984 chevy caprice... and make sure it has the regular v-belt pulley on it, not the serpentine pulley. (I've seen both on the same alternator!!)
Note that this alternator does not come standard "one wire." Rather it is three wire but can be run as one-wire by jumping two of the terminals on a stock 10 or 12SI. We can elaborate on that if necessary when the time comes.
