Buy an installed xupercharger WITH 3 year powertrain warranty, plus get the rear axle changed to 4.56.
The net result is MUCH quicker than the 05 stock SSR, for still a lot less money, as the supercharger installed with 3 yr warranty plus the rear axle change will cost you $7500, or $8000 at worst. You would have more peak power than the 05 (at least 350 hp even at moderate boost) and a LOT more low and midrange power.
The stock automatic transmission is not the storngest for this application, and that rear axle (the basic axle, not the 4.56 ratio) is also not the ideal, but if you use the truck REASONABLY (i.e. have fun but not abuse it), I doubt you would have any problems.
The only deterrent for me is he amount of actual one shot CASH needed. The ttal expenditure is actually not outrageous at all, but you need to divert about $6500 installed for the supercharger, plus $850 to $1000 for the rear axle ratio change, from wherever in ONE big chunk, rather than sread out as payments on an 05. I don't know about the rest of you guys, but with a son in 2nd year college, and a still unsold extra home in another state, I don't keep that kind of CASH just lying around.
Mind you, it's a great DEAL compared to the 05, as the $7500 or so is much less than the difference in cost between the 04 and 05.
I am starting to view the rear mounted turbo a little less positively, because:
1. With no specific kit being yet available for the SSR, you need to have a standard kit modified and adapted, which raises the cost closer to what a supercharger would cost
2. The rear mounted turbo doesn't produce meaningful power improvments below about 3000 rpm, and our heavy SSRs need the help BELOW that. The supercharger adds power considerbaly sooner than 3000 rpm, and is more linear with rpm than the turbo.
Jim G