We used the Alivio derailleur...
... on the original Sofrider, with Shimano Revo-shift grip shifters, in 8-speed configuration.
I can't see any reason they wouldn't work on a conversion.
They aren't top-of-the-line, but they work quite well and should serve you just fine. Most Shimano parts levels are equivalent on operational quality, they just differ in "bling" quotient.
Cheers,
Doug