I'm put our 71 charger back togeather. The I nt. Is still out of it
All the wiring is brand new one from year one. I have bolted in a super tuner 3 with a CD. But not wired it in yet
I'd really like to install a soundstream amp i held onto for years. Some good 6x9s and possibly 4 10s. Or maybe 2 12s
I have stock alt. Still. How much bigger then the 30 amp alt. Can I put in without worry about burning anything up?

Might want to get a generator and mount on a trailer to tow behind you. Really, you don't need all that for a really good sounding stereo, and I'm don't think it would be a good idea to stress a stock system with a giant alt.

Yeah I didn't think so either
But I don't think the o rignal 30 amp alt. Will power the amp I have. Very well. The amp is a 604 soundstream amp (4 Channel or one channel)

#1 is to clean ALL terminals/connections especially the main in/out wires/brass terminals in the bulkhead which you have a leg up on that with a new harness & ground paths are important also. I would relay the stereo directly to the alt. If needed, the non stock Denso alt setups get good reviews here. I cant say what your requirements will be.

Let me ask, what are you wanting? A nice stereo, or something that will make people in the next lane mad? I have a 71 B body, and without all of that stuff, I have a very loud, and good sounding stereo, and It all looks stock. Just because something is loud, doesn't mean it sounds good.

I don't care about hearing it thump 5 blocks away
I had this amp in my Durango with 4 10s in the back. And I liked it. Good. Crisp. And some clean bass

Il put it this way. The setup in my Durango was far better then my 14 ram (or my other trucks) our 300. Or even our hellcat with the 2k option system in it. Yes is may be loud (somewhat) but...is very lacking and a letdown for me anyway

How many watts per channel?

You could use the larger 50 amp I think ac alt, run a spare 10 gauge wire from output stud to battery positive, with fuse or fuse link,and hook your amp there. Use a good battery, and never let it get old and you will be fine. You should also install a cheap voltmeter as the ammeter will no longer be accurate. $2 on ebay. If you need more switch to a single wire 100-200 amp alt and 2 gauge ground and positive wire.

I guess I grew up in the great stereo era too....I used a powermaster 75 amp alternator and then ran an additional 10 gauge bypass directly to the starter relay{complete with an "extra" factory style fusible link...All stock wiring, original circuits including the amp gauge intact...Instead of the stock battery terminals I used Raptor terminals and ran the stereo wiring from those through an unused firewall hole and back to the trunk to the distribution blocks...Two 10s in the trunk,two amps in the trunk 6x9s in the rear deck,kickpanel speakers, and 4 tweeters in the cabin...Used the original fuse block for the head unit only...
No capacitor for that build and the lights never flicker when the bass hits..I built another system and used a capacitor mounted in the trunk to keep the low amp alt from taking the hit with subs and it's held up nicely in that vehicle...

I do have a capacitor that was removed from a system wife had in her truck. But don't know much about it other then leave it alone lol

My amp is a 604. 600 watts 4 channels. Or switchable to 2 or just one channel

Capacitors need attention occasionally....Usually a capacitor will have a resistor supplied with it...If, for any reason you need to discharge the battery {as in disconnect the battery terminal} you need to discharge the capacitor also before working on the vehicle..And in turn when you reconnect the battery terminal that supplied resistor goes in place of the capacitor's fuse so it charges slowly up to 10-11 volts{+ or-}then you pull it and slide the fuse in and it's ready...
But I'm thinking a 30A alt is just too small even with one to level out the spikes...Might as well upgrade and save the drama down the road..Literally...

I do have a capacitor that was removed from a system wife had in her truck. But don't know much about it other then leave it alone lol

My amp is a 604. 600 watts 4 channels. Or switchable to 2 or just one channel

Factory alternator off a mid 80's 5fth ave is 78amps !! . . . can get with dual groove pulley . . . for stereo I would wire separately to a relay to provide the power to stereo, that is control the relay off the std wiring harness, then power up the stereo from the battery, thru a fuse, thru the relay . . .

Cheers,