Another way to go - if you don't care about the old PC mobo you're salvaging from - is to use a propane torch or a paint stripping heat gun. Do this outside! but clamp the mobo into a vice, put a dead ISA card in the slot, heat the mobo from the solder side. When it's ready, yank the connector out with a pair of vice grips. The dead ISA card -or better yet, just the edge connector from one- keeps the plastic from deforming under the pressure.
Then you can saw the connector apart and get the 16-bit extension part. Personally, I wouldn't remove the Amiga's whole ISA connector. Why invite trouble... Some of the 2000's I've seen had filled holes for the ISA extension. You'll need solder wick or a vacuum bulb for those.
