>Maybe this is a crazy suggestion, but a good ol' resistor-zener power
supply
>is really really small, and really really simple.  I use a resistor-zener
>power supply on oven controls all the time.  So the regulation and ripple
is
>crappy?  PICs don't care.

I would be very tempted to include a constant current diode as part of the
resistor chain. If you selected a diode with current rating of say 1.25 to
1.5 times the current draw of your block at say minimum supply voltage plus
10%, then the worst case current draw through the zener will be the current
diode rating, possibly allowing you a higher margin of safety on some of
your power dissipation. I was looking at some recently which had 100V
ratings so they would survive your 80 volt test.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.