I have radials on my '37, it will run 75 all day long with the 250, but I tend to stay around 65. I know the truck won't like an evasive move or lane change, even with all the improvements I have made.
The wheel you run were made when speeds were way slower, are they riveted together? That alone would make me think about speeds, straight-line would be OK, but what about a hard turn or heavy pot hole. Maybe look into a second set of tires and wheels, long distance driving for the newer ones, around town for the OEM's.
My biggest fear is the steering column, three point seat belts were a must have.
