I too would be careful with 8spd, they could be wider than the 6/7spd the hub was made for. Never tried one myself though. My suggestions would be:
Dura Ace 7400 (hard to find in MTB specific gearing, no Hyperglide means average shifting performance)
Sachs/Maillard Aris (the "LY" moniker was just the designation for the different tooth counts, LY=13t; superior sealing; no HG)
But just about any cheap 7spd shimano freewheel should fit (horrendous looks, but shifting is best on these thanks to HG tooth profile)
They all will be relatively heavy, offset by the lightweight hubs.