Schrader's was selling adapters for 390/429 valve covers and someone had some adapters that would allow the use of Ford 460 valve covers.....not sure who sells them though.
Potter has an aluminum valve cover that's pretty nice. I'm thinking of getting a set to replace the cheap chrome set that I have now.
As far as the cheap chinese ones that are like $25 on eBay or summit... as terrible one already pointed out they're too small for most non-stock rockers. Some have been reported to not have a baffle over the PCV filter hole so oil can get up on the filter, this isn't a big issue to fix though. Then again I have seen a pair that were cheap but looked slightly different that did have a baffle.
Oh, and Flash/CadCo sells extra thick valve cover gaskets to help with clearance... might help you fit those rockers in there T1.