Yes, they all work fine with 8spd cassettes. Shimano rear mechs have a top jockey wheel with 0.5mm of movement which helps shifting when going from 5.0mm spaced 7spd cassette to 4.8mm spaced 8spd cassettes.
Set the rear mech up as normal then connect the cables and chain and it should work fine. Many people have been running this set-up for years without issue.
Just to add, I also use the older 6spd Shimano thumbies on 7spd as they too have the 'extra' click.