This is a very old thread, but thanks Patrick for the very clear wiring instructions for adding emergency flashers. Since this thread is still relevant to anyone wanting to add flashers to their car, I thought I'd add some detail about how I mounted mine.
I went with a marine toggle switch and mounted everything on a 1" wide x 1/8" thick steel bracket that I fabricated from my collection of scraps. There is a steering column bracket directly behind the dash and the bolts sticking straight down are plenty long enough to add the bracket and a couple of new nuts without having to disassemble anything. That's what the two holes at the end of the bracket are for.
The photo below shows the bracket mounted to the steering column bracket and extending to the right. I assume ERA made those bolts extra long to make it easier for assembly. Regardless, it sure came in handy for this. I made the bracket long enough to mount the switch directly behind the horn button so it is easy to find even though you can't see it.
This was a fun little project, so thanks again Patrick. Now, here's hoping I never need to use them...
Kevin