2003 Alternator problem

[2500HD]

This morning I jump in the 03 silverado 2500HD with 6.0L and try to start it and it is ticking away like the battery is dead which is funny since I had just driven the truck like 12 hours before this. So I jump start it and take it to work, go to leave work won't start again get a buddy to jump start it. I take the battery out and have it tested at the auto parts store they say the battery is shot, buy a new battery put it in truck starts up fine. I take the truck back up to the parts store to have the check the alternator the whole way to the auto parts store every time I stop at a stop light the battery gauge drops way down and come back up they test the alternator and say it is only putting half of the amps out it should be. So they check to see if they have an alternator which they don't however they have two different ones for my truck a 105 amp and a 145 amp. Now I know you could get dual alternators as an option but I don't have that and I am not sure which one I should get cause i want the one that is going to fit so does anyone know what the stock alternator is for a 2003 2500HD with the 6.0L engine?

[Rumpamuro]

the 105 one and 145 one both fit, one just simply pumps more power, if you have alot of options, youll need the 145. Everytime i need to replace an alternator, i simply call the dealer, and give them the vin# if theres more than one choice. id go with the 145 personally, especially with that big 6 liter.

Its like a new house, when the electrician comes in to wire it, they have to decide what kind of system the house will need, a 100A or 200A he makes his decision upon how many sq.ft the house is, how many appliances, and any other high current draw accesories.