For every hour of driving you'd have to make up the $60 difference in hourly rate, which means you'd have to travel 60/.52 = 115 miles per hour.
It's possible the mileage would be reimbursed, but not taxed in which case you'd multiply the numerator by 1 minus your marginal tax rate. You'd have to be at something like a 44% marginal tax rate to make break even possible at a 65mph average speed. If it isn't taxed it probably wouldn't be subject to FICA, state, or federal taxes, so you'd need to look into that.
I'd say unless you have a pretty high income you're probably better off taking the $75/hour.