I've had my 05 for a few years now, but with home ownership it's been parked for about six months. Finally got to a place where I could fix it and started diagnosing. What's happened so far:

AC/Heat stopped working, and typical P0410 code
Car sat for a couple months
New battery (old would not hold charge)
Replaced blower motor resistor (AC now works)

When I went to drive to get the car inspected, upon startup, all the ABS ESP etc lights lit up. I went ahead and drove it around to block to see if it was just swapping the battery. Rear brakes would not engage (surface rust still on rotors), and the front brakes are scraping (noise and excessive heat from sub 20mph driving). Also the speedometer is not working. I bled the brakes once everything cooled down. The front calipers bled fine, I went ahead and reset the calipers. The rears would not hold vacuum or bleed. After about 8 mins of bleeding I got 3oz of fluid out of the RR.

At this point I think one of the control modules is bad (non-functional speedo) and a failure is somewhere on the chain for the rear brakes (bad caliper, bad line, or failed master cylinder)

The crossfire was my daily driver, so in the meantime I've been driving my old motorcycle rain or shine. Any guidance or advise you guys could lend me would be much appreciated.

 

A failing RCM can cause in a long list of issues to include a malfunctioning speedometer. The easiest thing to verify whether there are any issues with the RCM is to switch it out with a known good unit. If you know someone else with a Crossfire nearby see if they will let you briefly try their RCM in your Crossfire. Otherwise, do a search on RCM repair and look into whether the individual relays are functioning properly. For example, you might have poor solder joints, dirty relay contacts or a bad coil on your traction control relay.