I've got about $250 to spend.
I can't decide which combo to go with.

1. 2" rear lowering shackles, MSD spark plug wires, Lakewood traction bars,
and 6.0L engine cover OR

2. ASP crank and Alternator pulleys

Which should combo should I go for??

 

Go ahead and do the cam. I'm pretty sure you should be able to find a used comp 212/218 and springs for $250. Ive seen several go for less. Linenfelter sold one on ebay recently for around $170.

 

cam is a good mod. you might need tuning to get it all together right. if you are torn between what you have listed then go pullies.

 

Most guys thar run that 212/218 cam gain over 30 rwhp. On a 99 that has the smaller cam, you'll likely gain 40 rwhp. No other mod will come close to that for $250.

 

out of the two options you mentioned, i would go with the pulley. but you should really consider big tex's choice

 

Where could I find this cam, what are the specs, would the HPP3 work with it and would I need better springs? How much does it generally cost to have a cam and springs installed, because I looked on the "how to" web site and It looked very technical. How much mpg would I loose?

 

You could find this cam in this site's classified. I was able to get mine for $175 with less than 3k miles. You would need some custom tuning to get the most out of this cam but it's not neccesary. At least you will needing some some better springs(comp cam 918's) with this cam. Since your truck is a 99, I am assuming you have accumulated a great deal of miles. It is suggested to just go ahead and change the gaskets, timing cover seal and timing chain.
You can get this done for about $350-$550. Some people will do it cheaper but really it's up to you. After getting my cam and tune installed I don't think I lost any mpg. In fact, I think I gained some.

 

I'm almost at 51K miles

 

gmc5.3L, don't have it installed at a shop in our area....you'll pay atleast 350. there are several local guys that will install it or help you install it much cheaper. Slowverado@yahoo.com is my email if you do get a cam i'd help ya install it, or we could do it at my shop me and my buddy that usually helps me with cams can get one done in about 4 hours if we have all coolant and gaskets and stuff before we start.

 

I woudl at least say don't go with a used set of springs. To me that's like putting a hand grenade with the pin pulled in your engine. You have no way of knowing how hard the springs were run before they were pulled. A used roller cam can be cleaned up if it has any minor imperfections.

I've known guys to get 15-20 HP off of a spring change alone, that woudl be something to consider. With better springs in the motor that raises the ceiling on how much you can do cam wise.

I definitely agree with the above, that basically a cam/spring move would be the best way to go.