I don't have a TF truck, but did put monoleafs on my '51 AD GMC. I honestly can't tell much difference in the ride, but the old springs had been rebuilt and gas shocks installed, so there wasn't a very good basis for comparison. There is very little arch in this kind of spring. They are almost flat even with no load in the bed. This is why they will lower the rear up to 4" depending on how worn out your old springs are.

As for load capacity, I have hauled a fully dressed 261 (I would guess about 700 lb) with no ill effects. Since the single leaf is thinner at each end than in the middle, the leaves went almost completely flat, but didn't change the ride height much if any. I was careful not to hit any RR tracks or potholes. Whether the monoleafs would hold up under repeated heavy hauling I can't say. For occasional use they seem fine.