70 to 75 won't do any favors for gas mileage, but I have an equally equipped '69 that has no problem running at that speed. 95 is about all I've ever done, due to traffic and the fact that I have manual brakes.
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'68 Dodge Dart 270, 225, 904, 2.76--"Lucy"
1996 Gmc 1500 Z71, 350, 4l60e, 3.73s
1995 Jeep Wrangler Rio Grande 2.5, AX5, 4.10s
1989 Toyota Pickup 22re, auto, 3.73