I went through the same math and decided to go with a TKO-600 with 0.82 OD and a 3.54 rear. I also considered a 3.31 rear. The numbers are as follows:
* 3.54 and 0.82 with 26.6" tire run at 2400 RPM at 65 MPH and 71 MPH at 2600 RPM
* 3.31 and 0.82 with 26.6" tire run at 2200 RPM at 65 MPH and 70 MPH at 2400 RPM
Keep in mind my engine uses solid rollers and is optimized to rev a bit higher (up to 7200 RPM). Also, these engines have so much torque that I didn't feel the need for 6 speeds.
Here is the Tremec calculator, FYI:
http://www.tremec.com/calculadora.php