I recently converted a '64 El Camino from Powerglide to a 200-4r.
I bought the trans,torque converter,crossmember & TV cable setup from Bowtie Overdrives.
The El Camino has 3.08 gears and 26.4" tall rear tires and in overdrive is only running a little over 1600 RPM at 70 MPH.
I feel that this is too low of an engine speed. I think I'm going to change to 3.73 rear end gears soon. This change should bring the RPM @ 70 up to about 2200. I considered 3.55 gears, but decided on 3.73's so I could go up a little on the rear tire diameter without getting back gown too low in RPM @ 70.
BTW. I ended up not using Bowtie Overdrives crossmember, for two reasons.
1. It seemed a little wimpy.
2. It was a little crooked.
I welded a piece of 1/4" angle iron to the frame at the appropriate spot on each side to be able to use the original cross member. Of course, that may not be an option with your Nova, being a Unibody car. The El Camino has a full frame.