I ran a megasquirt MS3X(build it yourself version of the PRO more or less) for awhile with a carb. If you install the sensors you can log whatever you want.
In my case I used for ignition control as well. All my MSD stuff had failed over the years and since I was going EFI anyways I opted not to replace it. I used the megasquirt to control the ignition and datalog air fuel, coolant, and air intake temps. It was great for ignition control, my drag week average was about .1 faster than it ever had been and I had made no other changes. I just put 80 miles on it this weekend with the full EFI working and its easy and works great.
The ONLY thing that you would need to different if using it as just a logger would be the RPM signal. You would need two sensors on the crank to pick up RPM, one for the megasquirt, and one for your ignition. I am sure there might be another way to trigger it, maybe even off the MSD tach signal but I didn't intend to use mine that way so I didn't look into it. Check with the guys at DIYAutotune.com.