For a 6.2 with a Whipple 1 3/4 or 1 7/8

 

1 7/8

 

Ok will that be better for torque horsepower or both

 

Both..

 

1 7/8" primaries.

But for your money, buying 1 3/4" will likely get you farther. For example:
my 1 3/4" stainless LPP's - $500
my used GT2-3 cam, LS6 springs, and gaskets - $400
my tune - $300

So for $1200, I got LT's, blower cam and a tune (already had a tune, just making a point). OR for $1200, you can get 1 7/8" headers. All depends on your budget.

 

A good set of headers goes a long way

 

I agree with TX tahoe. It depends on your budget 100%. That being said, there is LEGIT power to be had with a high quality set of headers over budget headers is you can afford them.

 

if the texas speed 1 7/8 will fit your truck, it is a GREAT budget header. seen pictures of them side by side to 1,000 kooks headers and every bend looks identical.

 

I'm getting American racing headers 1 7/8 with cats

 

Smart man. I thoroughly dislike budget headers, for several reasons, including poor fitment, no cats, and crappy connections resulting in leaks and wasted time under the truck. ARH all the way.