If I remeber corectly, the "Q" version of the Borg-Warner o/d was used with the later full syncro SM 326 trans, and is slightly shorter to keep the same overall length because the 326 trans is slightly longer than the 318. Either one will fit, I've read that the 326/Q version is stronger than the 318/H. I have the 318/H in mine, love it. red58 is right about the electrics, especially the solenoid. And new ones are not being made. You can fake it on some of the peices, however. I used a 50 amp rated headlamp relay for the activation relay, I also installed a switch to cut power to the relay when not in use. The wireing harness is readily available from most aftermarket sources, the are meant for v-8, but will work with 6 cylinder with no problems.
In my area, the average selling price is $100-150,US.
