Auto Parts: glass packs

Question
I have a 1983 ford bronco xlt with a 351 windsor and an c6 automatic trans. I want to install a set of headers with 2.5 inch collector tubes and 2.5 inch exhaust with glass packs. I will exit the exhaust before the back tires. That means a need less pipe but I am not sure if the amount of pipe before and after the glass packs will affect the sound. Would i better off with 2.5 or 3 inch? My engine is compeletely stock, but the holley 4bbl. I also want to install a camshaft and a high performance intake manifold. Jegs and other sites say that it is best to change your valve train also due to the aggressive lobe on the cam. Do you think I need to change that because I just want the parts to improve fuel mileage for when i decide to lift the truck? I am tring to get more bottom and mid range power than top end. I do not plan to be on the strip. Maybe play around in the mud a little. Thanks!


Answer
    The closer the mufflers are to the engine, the quieter the sound coming out of the pipes.  I don't know why, but it's true.  You would be much better off with a 2.5 inch exhaust.  You won't get any benefit from the 3 inch exhaust unless you crank the engine above 5000 RPM.  And it would cost you a bug pile of money to replace all of the parts you'd need to get the engine to do that.  Before you start throwing parts at the engine you need to consider how many miles the engine has on it.  Anything over 75,000 and you should be rebuilding the bottom end as well.  This could end up costing a lot.  If it was me I would put on the headers, an intake manifold, and the Holley carb.  Then do whatever you were planning to do to the suspension.  If you are really disappointed with the power at that point, then you could go after the powertrain.  Find out what gear ratio you have in the front and rear axles.  If it is lower than 3.56, then boost it up to 4.10.  A shorter set of gears will make a big difference in the torque that gets to the wheels.  I changed my old Lincoln from 2.73 to 3.90 and I was dusting off 5.0 Mustangs in a 4500 lb car.

    If you get to that point and decide to do the engine, spend some money on better cylinder heads.  The stock 351W heads are the choke point on the whole engine.  Pick out a cam that you think will work well, and then buy the next size smaller.  People always buy too much cam, I learned that the hard way by selling them.  You'll want a roller valvetrain and the tallest dual-plane manifold you can find. Edelbrock's Performer RPM is a good bet.  And you'll probably need to get a 1" spacer to run underneath the carb.  The extra plenum volume that it creates will increase low-end throttle response.  Use an MSD ignition, with the box.  You don't really need the extra spark to make power but it will run much more smoothly at low RPM's, such as at idle.  Make sure you use good quality parts on the rebuild, Melling oil pump, Cloyes timing set, and Fel-Pro gaskets.  And use a K&N air filter, you should buy that now 'cause it will help at all engine speeds and power levels.  If you have another car for a daily driver, buy a K&N for it, too.  they're that good.  And have fun.