the playfields do actually have the game name on them - at least the ones I've looked at. It's conveniently (cough) printed on the top surface of the playfield in the lower right area just below where the artwork ends.
the bottom arch is nailed on from the bottom side, so it's easy enough to pry off and whack back on using the existing nails. Plus, you get to see some of the original ink colors.
generally the wiring is the same color, ID and in the same places on the plugs from game-to-game of the same game type, and the differences are usually wiring going to shutter switches.
if you had to get a wrong playfield to complete a machine, as long as it:
- had correct rollovers (if needed) and text (if any)
- the jones plugs were big enough/too big (you can cut them down to needed size)
- you had some parts if you needed to add switches to the shutter
you could make it work assuming there's no oddball things required (bump/hold feature bits, magic pockets, extra hole switches, etc.). Moving wires around on the jones plugs is easy if necessary.
you shouldn't rely on the wire colors matching, tho. The only safe thing is to compare the plug charts and schematics between the two games to ensure the wires are going to the same place and the circuits are the same.