I once put radials on the back of a '57 Froid I had & kept bias on the front. They didn't stay on long, squirliest thing I ever drove.
Same thing here Tiny, I had a VW bug with radials on the rear and bias fronts.
Here you were allowed to mix bias and radials but not on the same axle,and as long as the radials were on the driven wheels.
A road trip along the winding roads on the west coast in the wet was the scariest thing ever!
Can you say understeer.......