theres no where near enough valid info to give even a random guess, you need to post a good deal more info about your cars engine and drive train, is it a 283 or a 350 or a 406 SBC ??
are you running a high or low compression, a flat tappet or a roller cam, what carb are you using, what plenum vacuum, are you seeing at idle?
what transmission will you use?
if its an automatic what stall speed on the converter?
without knowing the cam,lift & duration and LSA, cylinder head flow rate, engine displacement and compression, and the specs on the headers , 1 5/8" shorties? full length 1 3/4"? and the exhaust system back pressure at 3000 rpm, being used you can,t reasonably predict the engines potential power curve, with out the rear gear ratio, tire diameter and transmission gearing your can,t predict the engines potential, useful torque in the intended rpm range. .
and if your only really concerned with the torque curve below 3000 rpm I doubt there's much to be gained with an intake manifold swap, between those two intakes
http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
http://garage.grumpysperformance.co...hing-the-drive-train-to-the-engine-combo.741/
http://garage.grumpysperformance.com/index.php?threads/dynamic-vs-static-compression.727/
http://garage.grumpysperformance.co...lsa-effects-your-compression-torque-dcr.1070/
http://garage.grumpysperformance.co...llecting-cylinder-heads.796/page-2#post-57825