I presume it has stock injectors? 366 is way too big. It is possible to make nearly 700hp with a big turbine SX-E 366. He will be a lot happier with a small turbine 362. We have run a number of 362, 363, and 364.5’s with the 68/76 turbine, .83 turbine housings, on Irate T-4’s and really like them. We usually run the .83 housing to aid spool up, but this is on trucks with 3.73 or 4.10 gears so with 4.88’s or 5.13’s I’d run the .91 housing to slow the turbine down a bit when cruising. Have whoever tunes it set the tow/haul button to lock out overdrive and rock on. The stock downpipe, hot side intercooler pipe, and intake will fit perfectly with this setup. I always wrap the up-pipes with DEI Titanium header wrap and run at Turbo Performance Products turbine blanket. The Borg Warner part number for the SX-E 62/68 is 13009097056 and the part number for the.91 housing is 177207.