Never ran a Nash, but I hear their great. As for calculating the ratios, its really pretty easy. I searched the web and found no less than 12-15 different (and free!) calculators and I input my numbers to determine my highway speed vs the necessary gears I would need. After several attempts (I couldnt believe my eyes because Im running a ZF-6 speed out of a ZR Vette I found at a swap meet) I finally opened up excel and built my own. (I'll send it to you if you email me and ask).

To my surprise, the other calculators were right after all. With 4:11s and 30.5" tall tires, I still have to run 75-80 mph to justify 6th gear. 4th is 1:1, 5th is .75:1, and (sit down for this one) 6th is .49:1. In fact, at 100 mph, she turns 2300 rpm (barely awake). So you can see just how streetable a stout horse can be. No one believes me about the gas mileage so I wont even mention it (until we hit the road and they see the gas going in and the miles coming out that is).

So I guess I would recommend putting your money in the tranny and keep your ponies. You can have your cake and eat it too!