If you really want a V6 turbo, put a 3.8 buick (gn, gnx, 20th anniv. TA) or 4.3 GMC (syclone) in it
Any one of those can make some serious power! However, we have fat pigs to contend with
so don't expect the same kind of performance #'s, he he.
I like thinking about different possibilities, but when it comes to these, since there were V8 options already, why start at the bottom. There were so many of these WK's made, it would be better to start off with a more stout platform and I imagine the drivetrain is a little more H-D, as well as cooling, etc. already [not saying they will put up with it, per se, but least it's an upgrade already there]
8 psig is pretty low boost and especially on a small engine, like the 6 cylinder...You could probably run more boost with a well designed intercooler and some sort of water/meth injection and really creative tuning, but there comes a point of no return (on investment)...
Personally, with so much weight to lug around, you want to focus on low to mid range torque and being our engines are so small (even a 6.1 in that respect), I'd personally rather go with a supercharger than a turbo...don't get me wrong, I like turbos (my gvr4 puts out ~400 hp and well over 420 ft./lbs on a little 2.0, but it only weighs 3,200 and I run 22-24 psi on it), but the heavy pigs do not mix well with needing to spool up the turbo to get the power.
Also, we are limited on being able to use a really efficient compressor (turbo), since it has to be placed so far from the source and it will lose some of its needed heat energy. Partly why engines like the 4G63 (mitsubishi 4 cylinder turbo) can make so much power relatively easy. You want as much heat (the expansion) to get to the exhaust turbine as possible...Sure, it *works* in other places (liek the STS), but you also need to have so much routing to, thru and past an intercooler, you also get more pressure drop and probably soaks up radiant heat from the engine more, too.
Another consideration is gearing. Don't the V6's have 3.08 diffs? That's gonna really work against you in acceleration, except when you're on the highway, but then we have our brickdynamics.