Great idea and the GT3 motor is a much more robust engine but I don't think the chassis and necessary modifications are worth the effort / cost. Apparently it's not a simple swap to put the GT3 engine or a 3.6l engine into a 3.4l car like mine. There are companies that increase the displacement of your 3.4l (flat six innovations) and upgrade the internals but it appears that is a $15k endeavor. The chassis is not worth that investment IMO. I think I either sell the car as-is, buy a used 3.4l motor, or have mine rebuilt. I'm trying to figure out the best option and I need to determine who is qualified to build these engines. I want it done right if I rebuild....
'04 E46 M3 - Jet Black - Sold
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'13 E92 M3 - Alpine White - Ohlins TTX, Fall-Line Suspension Arms/Bushings, AP Racing BBK, OE GTS Aero, Cobra Seats, Akrapovic GT4, GMG 4-point, BBS E88