Yes left as they were originally built..... that by itself would be a very effective speed limiter. I decided to eliminate that condition when building my truck. It can be done. At 65 mine is on a par with your average 10 year old pick up truck.
Cruising at legal road speeds in heavy traffic is doable but in my opinion there are several mod's required to make it an enjoyable experience. Gearing, brakes, suspension and soundproofing all need a fair amount of attention if that is the goal. The real limit to top speed in a Pilothouse is the unfavorable power to weight to shape equation.
Jeff