Found the calculators. Stock tire size 55mph=2566rpm, 65=3032, 70=3265 - Tire size of 165/80 15 55=2300, 65=2718, 70=2927. I was surprized to find out that it takes little more than a 1/2" height to decrease over a 100rpm at speeds of 70mph.

Looked through the owners manual. The above figures are for a 78 B210 Hatchback GX with a 5 speed 3.7 diff, .854 (5th gear).

With this info I found that my speedometer is incorrect, I have been cruising around at about 62mph thinking I was going 55. Happily I have not been issued a citation. Anywho, any ideas of how to fix my odometer, especially if I go to a taller tire?

For the power issue, I just think I will shift into 4rth if needed. I do have a weber, I just haven't decided wether to install it or not.