Vintage cars often times have inherent restrictions for everyday use, just because they were not designed to go at the speeds of the modern vehicles. Far to often, people want to completely modify the drive train in order to make the vehicle function adequately at modern highway speeds. In doing so, they loose the entire character of the vehicle. I retain as much of the original vehicle that I can, while making it function in a practical manner with today's standards. Using the old stuff is always going to be a compromise when it comes to comparing to modern car function, but then, if modern is what you really want, you should just go out and buy a modern car. It will save you a lot of money and you can start enjoying it immediately. Besides, you won't be destroying another part of fabulous history by purchasing that new car.
Of course you need to make sure your braking system is adequate for stopping from higher speeds. You don't need disc brakes to accomplish that either. I do prefer hydraulic over mechanical for the reason that the hydraulic braking system is somewhat self adjusting. Mechanical brakes require much more maintenance to keep them in adjustment.
Back to the original topic...
You can usually find taller gears for your rear end that will afford higher cruising speeds. This is by far the cheapest and least intrusive method when it comes to maintaining original character of your vehicle.
I have installed a Borg Warner R10 overdrive in the middle of my torque tube/drive line of my 1937 Chevy Truck and added the later 1941 rear end with hypoid 4:11 gears. This is a fabulous addition, as it allows you to split gears, virtually turning my upgrade 1941 three speed transmission to a five speed. This system requires a bit of machine work, after you locate that Nash or Rambler overdrive but it is the one that is set up for the enclosed drive line so you can bolt to both ends.
I have 35,000 miles on mine now and have fully tested it in continuous 100 degree temperatures during my solo cross country drive. 70 mph was the comfortable speed and that is what I maintained in the hottest part of my trip.
If you would like more information on this conversion, please feel free to contact me. I can do more explanation on how to set up the controls etc. See the pictures below.