With the Mach4s, manual trans and 4. 10s I'd suggest a full B1. Towing heavy I can get EGT up to 1300 pretty easy even with the Comp off. I disconnected the Comp today for a 3 day trip next week, a lot smoother throttle now with just the Catcher ECM.
Blue Chip makes a Redline box for higher power increases, and it's just fueling (not timing), and it's more adjustable...
I ran 215hp stock, 340hp before the MadECM Comp off, 434hp Comp 5x5 with and without the ECM. I'm gonna dyno with ECM and without the comp for reference next. Driveability improved having it removed versus turned off.
The htt turbos and the TAD B1s are all based on the Schwitzer with mods, I got mine before the htt stuff was available. I know the B1 from Turbo Auto Diesel (Ken Diaz) are nearly bulletproof-- important to me.
400hp setup with towing and street/strip power, almost perfect combo. I like the boxes for those taunting moments and dyno runs... hate the ricers staying close! Either way, get a turbo with a wastegate - external or internal - but keep it between 40-45psi boost for your head gasket and to keep the heat down.
DANG I talk a lot! Sorry