So, to follow up... [bracing myself for any criticism...]
I finished my manifolds. I was using 3/32 thoriated on one side, but switched to 1/16" and had better results. I used various sized gas lenses, finally settling on a #10 (!) with about 15CFH flow rate. I could not do continuous 90 degree beads on a lot of the joints like johnc suggested, most are 30-45 degrees. I had what seemed the least amount of heat when I did a little on each joint at a time, rather than completely welding one joint before going to the next. This also made it faster since I moved the weldment into position and then welded all the joints that I could get to. I also noticed that adding more tacks before welding greatly reduces expansion problems later on.
I ended up having about 2" (!) of tungsten sticking out and 17CFH on the hard to reach areas, with as much tape and argon as I could shove in to the area. I had a couple mishaps where I didn't get enough shielding gas, but by increasing the postflow (it's a fixed amount so I have to tap the pedal to get more), I could keep the bead and the tungsten clean.
I used ~10CFH pre-welding purge for one minute (or more on the larger pieces), then ~5CFH while welding. I say "~" because it's a Harbor Freight regulator and it seems to be going a lot faster than it indicates. Those low flow rates (at least) are probably inaccurate. Anywho...
I made the driver's side manifold first, then the secondaries, then the passenger side. I should have done the secondaries last, duh, but refitting after the manifolds moved was not too bad, luckily. I made the driver's side collector myself, and it was a lot more work than I thought, with the tools I don't have. So, I had Adam at Columbia River make the passenger side one, and was very satisfied (only $120 bucks!). His collector was a lot smoother on the interior, among other things...
Before you say it, yes, I plan on bracing the turbo with a heim joint. But I have a question, where should I place a flex joint? Do I really need one? About the only place I can see to place one is after the passenger v-band (as in, on the turbo side), where there's about 4 inches of straight.