How much FWHP should the boosted SHO be set at ?

I wouldn’t go any more than 350. That turbo is gunna make a boat load of TQ ~4500-5000 RPMs (closer to 400ft/lbs). You have so much $$ into that trany I wouldn’t risk it by putting down m uch more than 350 WHP. It’ll be pretty darn quick set at that #.