I don't have a Mk4 so I imagine if I order the gantry I'll just end up buying a 4 somewhere. The old can of worms.
If you have any other marks than the MKI, they will work fine. I have a MKIII in mine. I have MKI to VII displayed across two shelves with Tony, and so i don't want to spare the MKIV to go in the gantry.
After all, Tony used the gantry with the MKII, MKIII, MKIV and MKVI.
Even Tony works with the Gantry.