I also use the 5.50 X19 Excelsior Stahl Sport Radials.
Compared to bias ply, these radials handle and ride very smooth and "track" nicely, especially when crossing uneven or bumpy roads, railroad tracks, etc.
They have the added benefit of a little bit more tire surface area on the ground for better braking, due to the slight squatting to the ground compared to bias ply tires. While the radials cost about twice as much the bias ply, the tire life is supposed to be close to double the life of the bias ply. However, I cannot verify that as I only have about 8,000 miles on the radials, but they show no significant sign of wear so far. I will buy them again when I need replacements.