sorta, well, yes, you're correct, but, it is still restrictive, to an extent. i plan to make the new one from larger diameter tube, thicker wall, thicker flange and longer tubes before the collector. haven't decided yet if it will be a tri-Y header (or 4-2-1) or not, but the collector will definitely be at least a foot past the firewall. and yes, this will require some custom work to the rest of the exhaust system, but i will also have a replacement system available for this set-up, prolly sell it all as one package.
The best would be a long 4 into one using tubes about the same size or + 10 to 20% cross sectional area as the original manifold diameter. The aim for better low end torque is to maintain the exhaust flow rate and this is best achieved with only minor diameter modifications and longer runners. You are aiming to reduce the resonant frequencey of the exhaust system (similar principle to the long tubes on a wind chime). The longer runners increase the mass of gasses flowing through the runners, creating a more effective scavanging effect at low revs, allowing better cylinder filling with the new charge.
The side effect of this is you reduce the peak
torque, but it occurs at a lower rpm. This reduction in peak torque is also reflected in a reduction in HP at high revs.
Short pipes and 4:2:1 exhausts are optimised to suit high rev race engines (think - resonant frequency of a short runner). The runner diameter is more a function of the total mass of gases you are trying to dispose of, bigger for large capacity high rev sceamers, smaller for small capacity lower revving engines (remembering the requirement to keep the exhaust velocity up for scavenging).
There is a guy on Outerlimits4x4.com called Exhaustfix who would be able to give a few pointers...http://www.outerlimits4x4.com/PHP_Modules/phpBB2/viewtopic.php?t=69303&highlight=