Second Alt/ 3rd battery?

Alighty guys I have a couple questions.

I have an iraggi 300 amp alt but it is for a 5.7 I took it out of my last vehicle.

I want to put it in the dually but the problem is the the 7.4 has a 3rd bolt on the back of the alt and the 5.7 doesnt.
Is it an issue not bolting on the 3rd bolt?
maybe because there is more torque and horse power on these trucks?

Also what about setting it up as a second alt?
How complicating is that?

I have tried doing some searching on this but came up short to the answers I wanted.

Right now I have the 140 amp alt and 2 optima yellow tops and it doesnt even cut it...

I have 2 480s and a j/l 1000/1 and 3 12w3s and on the hard low notes it probably goes down to about 11 volts. It sucks...

I also have a kinetik hc 800 just sitting in the closet so do you guys think that adding that as well would work?

Let me know if anycombination of what i have would work. Also if you guys think I should do something different.

Sorry for all the writing and the help is appreciated in advance.

Thanks
Robert

i would add the HC800 battery .your electrical needs all the help it can get.... dropping to 11 volts is not good ..

you will need to fab up a mount to hold the stock and h/o alt right beside each other with a tensioner pulley... im sure you could find a place to make them. they are expensive though.. (have you contacted mechman.com ? )

how old are the yellow tops?
have you done the big 3 ?
#1-bigger ground wires from engine to chassis.
#2-bigger hot wire from alt to battery.
#3-bigger negative wire from battery to chassis

Yeah I was thinking that but... wasnt to sure if the combination of all of these would work and or work correctly. I didnt just want to through all of this at it if it isnt truly the issue if I can get away with less I would rather but ehh.

and no who what is mechman.com I will look it up but never heard of them.

I have sort of done the big three but I am going to redo with like some 0/ag wiring.

One yellowtop is pretty new not sure how old the other is it could be 2 years or 5 years. I cant remember which one.

Now will the alt work though?
Cause like I said it was made for a 5.7 I dont want the damn thing breaking off... I doubt it would but you never know. Gm did it for a reason right? Well I guess we are talking about GM so... haha

Thanks
Robert