Here's a couple choices. Like I said, I'm running the 46mm TB which is 650 CFM (or 750 with his 54mm), according to them.
www.sprperformance.com
Yes to all. For the best system, headers, single 3" (or double 2-1/2" with crossover) pipe, high flow Cat,(s) and straight through muffler(s), like my Borla Pro XS. I have a 2500 RPM stall Converter which starts just in its power curve. I'm running an 18 LB spring @ 20 PSI (you can order that spring in the TB from him) on my stock 61 LB/HR injectors, I'm getting 12.5 AFR @ 5700 RPM. I do have a little restriction there - instead of getting 100 Map, I'm seeing 90 - 95. That's why I suggested maybe a 50mm TB.
The Blue Print engine comes with 12cc pistons and zero deck for 10.1:1 with 64cc heads. With my 62cc ones I'm getting 10.3:1
The reason I'm pushing the 383 (or Blue Print 377 with 4" bore) is, I've tried flat tappet cams, and upgraded to a roller on my 350 (with the same heads) but, the 383 is miles above it in Torque and HP. Plan on getting a locking rear end (like a TrueTrack) and bigger tires for your truck. I can't keep mine from spinning until 2nd gear (with an open Diff and 375R60/15 tires) or I let up on the go fast pedal. If I
SLOWLY feed it the pedal without spinning, I'm getting ~7.2 seconds 0-60. HTH