Regarding speedometer accuracy, I have made several multi-thousand mile
trips with my GPS turned on the entire way.  What I have found is that my
speedometer is off (registers about 4 or 5 mph less than I am actually
traveling).  At 3000 rpm in 4th gear I am going 60 mph; at 3200 I'm at 64;
at 3400 I'm rolling at 68 and at 3600 rpm I'm humming along at 72.  Of
course, I have had a taller fourth gear installed (either a .77 or .78, I
can't remember).  The tires are Dueler HT 205 70 and I keep them aired up to
40 pounds.

Of course the odometer is off as well.  When my odometer shows I've driven
100 miles, the GPS shows 105.

Warren Lail

88 Westy "Billy Bones"