I saw 67 mph once in my diesel Westy with the 1.5 Rabbit motor in it.
Coming down the hill into Laramie WY from the Lincoln Memorial on I-80.
And no, I wasn't drafting a truck. (That time.) Since I've replaced the
1.5 with a 1.9 NA, I've occasionally seen an uncorrected 74 mph on more
or less flat ground without a noticeable tailwind. Fuel mileage sucks
at those speeds though.

Jim