Heat detectors vs smoke detectors

[warrenshudson@xxxxxxxxx]

Our home has old dictograph heat detectors in every room, and every
closet. I want to start replacing some of the heat detectors with smoke
detectors, but the wiring in place is 2 wire looped from the panel then
to every detector, then back to the panel.  As I can not re wire every
detector, is there anything I can do to help the situation? I can put
in at least 4 smokes in the house on a seperate zone with new wiring,
but would it be reasonable to also replace the old 135 degree heats
with 135 degree rate of rise in addition to the smokes? Also, what
brand 24v 4 wire smokes do you all use? They will be put on a monaco
c-100 relay based (old) control panel.  Thanks a lot.