If you live out in the country get the T56
If you live in the city get the 2004R
I have the T56 and it sucks driving it around the "city" traffic
That's a good point.
The T56 will require some floor mods. It's even larger than the Tremec shown here. I tried to maintain the driveline angle, so I ended up with a pretty big hole.
Depending upon the donor source, you'll have $3K in it when you have it running. As Turna said, if you sit in traffic on I95 in Bridgeport or the Post Road anywhere, you'll wish you had no left pedal. If you will go on long road trips, the T56 will be a joy to drive.
To confuse you even more, check out the GoPro videos Built6spdMCSS has posted. The sounds alone made me want a gearbox in my Malibu. Heed the advice about the bleeder hose if you use the OEM-style slave around the input shaft.
I imagine you used some sheet metal and made your own cover to cover the whole back up? That 3k in parts only? And I will definitely have to check out those videos. Easy reference to find them? YouTube channel or he post them here?