Yeah you probably wont like a procharger on a big heavy avalanche if your looking for instant power. And a 4l60e probably wont like it either so i would swap in a 4l80e. Single 3.5" or 4" should be plenty for exhaust.

 

These guys are on the rite track.. For starters, procharger loves big stalls, gears.. If you are looking for that out of the gate tq, it is not going to give it to you unless you stall it, gear it.. So coming into a kit(procharger might be cheaper), but to get it to work like you want will cost money with the addition of gears and a converter.. Next is the tranys, in a big heavy truck it will not take long to pop even a built 60 giving them HP numbers you want to make.. A 80 would be the best bet.. Next you will need to look into fuel upgrades like a pump, injectors.. The OBX headers are cheap, have had fitment issues.. Try to track down some LPP's they are nice, are stainless at a good price if you do not want to spend the money for high end stainless headers.. The TVS will give you all the power you need, might not make the big end power like a turbo or procharger, but will give you the low to higher power band.. True duals or a single 3'' should be just find for that power..

 

I would think single 3" would be fine for now as well, just swap to the muffler you want, maybe even the next size up (3.5 or 4") with adapters to your current 3" to maintain flow closer to the level of a straight pipe and leave you with a compatible muffler size if you ever decide to up the size of the rest of your exhaust. Also, I'm going to jump on the MP112/122 bandwagon here; as previously stated, it will give you both the low-end torque and low-end price that you are looking for. And last but not least, I've heard of FI 5.3 Avalanches eating 60s like candy(just like every other fullsize GM truck/SUV with a backseat); I'd save the exhaust money for an 80E swap, then worry about your longtube/ORY adventures once you've put a solid trans behind your blown 5.3.

 

ru planning on gearing the truck with 35s?
ru wanting to make 550 at the flywheel?
First things i would address would be start looking into a 4l80e swap as well as gears and diff.
Procharger does not make power off idle, maybe in a light reg cab it may come on quicker. but if its in a heavy *** pig like yours, your going to regret it.
112/90mm/milled 243s/cam/free flowing exhaust. a combo around there might get u close to your goal, and have off idle power.

 

You guys are great... I'm now thinking that a true dual would be best... The borla pro does not come in any bigger then 3 inch... And I'm sold on those muffs. So the flt level 7 65e is out? How hard do I have to build the 80e to handle it?