If this is any help, I run a T-5 with ratios 2.95, 1.94, 1.34, 1, .63.
My tire diameter is 24" +/-, horsepower approx 200, rear 3.00. At 70 in
5th, rpm 2000; at 60 in 4th, rpm 2000.
My feeling after 12,000 miles- need to change the rear to approx 3.5.
Off the line, so to speak , is OK, but not sparkling. At 70, not enough
instant pick up. At 60, good acceleration, could be better. Really
pulls in 2nd.
If you interperlate between the 2 tire sizes, I think you will confirm
your 3.87 rear ratio with T-5 transmission ratios as a good choice.