I've read somewhere that you can immerse them in acetone and it will dissolve the adhesive on the mirror.

I have not tried it, but it sounds reasonable to me.

74 Challenger, bought it new. In 1978 I replaced the original 318 with a 446 and 727. Mild cam, Jardine headers, and Holley Sniper EFI.
New engine! 511" RB, Edelbrock Performer RPM heads, Eagle rotating assy, Comp hyd roller cam, Doug's 2" headers.