a complete 2jz-gte motor is hella expensive...they have n/a-turbo conversion kits. they are made by turbonetics
www.turboneticsinc.com and they come w/ a t04e turbo and take you from 225 hp to 320hp. there is more info the turbonetics website. just go there and read up. also another good website to know would be
www.mkiv.com it has just about everything you could ever want to know about your mkiv supra. also titan motorsports have tons of great parts for mkiv supras.
www.titanms.com . and they have a mkiv supra that runs a 1/4 mile in right around 8.5 seconds so they obviously know what they are doing and talking about.