I've done both. The spearco setup has an elbow that bolts into the intake. No fabrication required. From the looks of it, it is the single most restrictive part of your intake tract. It necks down to barely 1.5" on the bend. My car trapped 110.3mph with it and it had a bit more left considering the low boost I was at. I have no idea how such a piece of crap like that could run those speeds.
Before I went to the Powerstroke, I decided to relocate my throttlebody to get my response and drivability back. In the process I welded on a 3" elbow, angled it back slightly toward the firewall for turbo clearance and have been happy ever since. When it came time for the Powestroke, I think it complemented the rest of the 3" piping.
If you don't feel like doing the welding for the powerstroke IC you can always use the elbow from Turbonetics ~$50 and use a silicone reducer to make it work.
If you're using the Spearco kit you're all set, everything is there.