My car has a stock 78amp alternator, but I will be swapping in a 140 amp alternator from a different car. (car is an 87 Buick regal, new alternator will be from 90's caprice). Will this upgrade be enough to run an ed NINe.1 at 1ohm without adding more batts? The amps max draw is 160amps, but not sure what it will draw under normal use. I have the big 3 done in 4 gauge and a regular battery.

if you can get the 140 amp alt for your car, get the biggest battery you can fit under the hood and you should be good to go. with maybe a little dimming of your head lights playing at night at high volumes. imo

Wouldn't hurt to upgrade your under hood battery to something a bit larger with more reserve. Something not a wet cell.

got a batcap 800 you can throw in the back.

100 bucks, cant lose

Depends on how you set your gains. It will be "enough". Don't skimp on the big 3.