Garrett finally filled the space between the GT3582R and the GT4088R. The GT3788R uses mostly the same parts as the GT4088R, but with the GT37 turbine and exhaust housing for a couple hundred dollars less since they sell a ton of GT37s to diesel owners. If you always wanted a GT4088R, but wanted quicker spool, this might be the turbo for you.
http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT37/GT3788R_772719_1.htm
http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT37/GT3788R_772719_1.htm