Drill a hole in the middle of the cross part, tap, thread in a bolt, and try to turn it Fill hole with jb weld.
I hope all parties involved know those pistons get twisted in, not pressed.
I actually had to dick with mine AGAIN yesterday (2 long stories). This car is so rusty it's amazing, and as much luck is - all the fucking outter seals are gone. So...I made a fucking tool for it. 1/2" socket with an "L" bar welded on. Breaker bar makes short work of frozen calipers. It's a whole lot cheaper than rebuilt calipers. I was going to post it up anyways, since I'm so smitten with it.
Anyways, good score with the springs. My car ended up with some Eibach sports like that too, makes for such a nice yet low ride.