Regardless of what alt you install, the gauge won't be very accurate or reliable. And even with a 38A, the dash wiring could still catch fire, even if you don't try to pull that much current through it.
The best, safest, most-useable fix is to delete the stock ammeter, wire in a voltmeter (VERY easy & inexpensive), and install a good used 130A 3G with some fresh battery wiring. Click these & read their captions:
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