Why would you want to get rid of the 4R70W? With a Vortech at 12 psi, Ported SVO heads, the gears you have and a 3000 stall converter and good tires, that car will go into the 11s. For what you would spend putting in a T56, you are not going to go any faster and will have spent a ton of money doing the conversion. Here is a site where a gentlemen I talk to on other boards has his wifes 96 GT with Vortech and Ported SVO heads running 11.77 @ 116 mph with an Automatic.
www.Hartracing.com. Go check it out. I'm in the process of having my converters' stall bumped to 3200 rpms so I'm in the boost off the line which should make the car fly with traction.
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99 Silver GT
4R70W, Borla Cat Back,
SHM Slotted Rotors, custom 10.5" ProTorque 2600 stall converter, Transgo Shift kit, Redline Synthetic ATF, Cooler, Bassani X-Pipe, Vortech V2 S-trim, 3.73 gears, 70 mm T/B, Mac Adj. uppers & lowers, ROH ZR6 17X9.5 & 17X8.5 with Nittos, BBK(Walbro) 255 pump & FMS Shorty Headers, D&D Tubular K-member, Coil-overs, & A-arms. Currently running 3.33 pulley at 12-13 psi with AFM powerpipe, but not dynoed yet.
Dyno:
316 rwhp
332 rwtq
Dyno 3/26/00 After fuel mod, FMS headers & Pro Torque Converter.(RUN #6)
338 rwhp
342 rwtq