Altenator/Regulator modification question.

[Sooner1970_K10]

Long story short my truck has no juice. For the past couple of months I have not driven my truck and have made it a point to go out and let it run for 30 mins or so every other week. At first it was doing fine. Starting up on the first key turn and purring to life. Then slowly it seemed to feel a little sluggish as the winter progressed. A couple of weeks ago I went out and it was dead, dead, dead. I jumped it with my little 02 Honda Civic and let the truck run for an hour or so. If I turn it off and then try to restart it, it starts fine. However if I leave it over night the truck wont start. Is this a battery or altenator problem?

Question: I called to find out the price and availibility of a new altenator and was asked if the trucks regulator was original (external) or had been modified (internal). I have no clue?? Can anyone tell me how I can tell if my truck has been modified? Should I look into replacing both the battery and altenator or just do the battery first? Napa has a new lifetime warrantied altenator for $69 bucks.

Note: I did a basic altenator check (I think) according to what I have heard, you can take a then piece of steel or a steel butter knife and hold it close to the altenator. If the altenator is good it should have a magnetic affect on the knife and pull it to the altenator. If the altenator is bad it will not pull the knife. Can anyone confirm this method? I did try this and the knife was NOT pulled towards the altenator.