bikeworkshop
Senior Retro Guru
Seem to remember the LX/STX stuff working pretty well -I do strangely have a long cage XT hanging round -would that supplement, does look a bit modern though...well, 90's anyway.
most mountain stuff was black or grey, or dull silver, but there's quite a few SIS- compatible polished silver long cage road dérailleurs, mostly from the 9 speed era, tiagra, 105 and ultegra, to give a classic look.
Jockey cage could be washered if it needed a little more space for the chain, but as a rule shimano hg40 6,7,8 chain works in a 9 speed derailleur, and on many 5 speed freewheels.
Ah the golden age of compatibility