Are you thinking about replacing them with radials? Replacing the split rims too? That size tire is still available in 8 or 10 ply bias. Your old trailer will love 'em.
Yes, I will get rid of the split rims too. It sounds like you are saying that these tires would be better than radial, is this correct or are you just curious? I know this tire size is still available, but knowing the modern size would give me more choice.