Easiest way to get my truck up to like 65 or so on the highway

[ahshoe]

I have a finished 1956 F100 with a very nice running 2 barrel 292 Y block. Been driving it for about 5 years now off and on during the spring, summer, and fall. It is a factory 3 speed that I converted to the floor. It has a 60’s mustang 8 “ rear end with a 3:25 traction lock rear gears. It pretty much maxes out at 55 or so mph with quite a lot of rpm’s…….Question: Is there any options to get this to cruise at say 65-70 on the highway without converting over to an AOD automatic transmission? I am open to doing most anything to make this more of a highway cruiser.