If it were me, I'd take that money and spend it on a doubler. Torque at the top of the driveline will mean that the rest of the drivetrain is going to suffer more strain while torque further down the drivetrain means everything upstream will suffer less strain. Primarily, I am talking about the tranmission since the A4LD doesnt really last that long on average. And if you have $$ left over, then regear the axles to whatever deepest gear you can find (since its a trail rig after all).
In addition, say this camshaft and exhaust gives you 10% more torque. Well a doubler gives you 140% more torque for probably the same amount of cash
And in reality of off roading, you want peak torque very low on the RPM band since you'll already be spinning tires at higher RPMs (which means more torque wont do anything). I'd look at the specs (torque to RPM graph) for that new camshaft first to see if that extra torque its going to give you is even within the RPM range that you off road in -- cauz if its not, then the most you might get out of that camshaft is an unstable idle.
As for the headers, I would save the cash because power/torque isnt about pipe diameter but exhaust velocity -- like engines with forced induction. Plus I think most of the advantage of an aftermarket exhaust will probably, again, be outside of your normal operating RPM range (since this is a trail rig).
Overall, if you really want torque, I would suggest you either get a doubler, or swap to a diesel since diesels have gobs of torque at the lower RPM range. And dont forget to reagear
untill i get some input on what to do to the motor.
