That's sick! Post a sound clip when you get that puppy in, I'd love to hear it!
Also, In my experience you dont need to swap the whole wiring harness. i just swapped the sensor from the 3 wire speedometer that came on the 99 5mt with the 2 wire speedometer that was on my 95 4EAT and spliced in the speedo, reverse and clutch switch to tell the ECU it was in nuetral when i pushed the clutch in and it worked fine. granted that was 9 years ago so i maybe forgetting something.