MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
24v heated beds are much "fast" to reach final temp. Also, 12v applied to a 300x300 bed would take forever and the max temp it can reach would be around 75 degrees.
Check YouTube, Scott has made a video for ramps conversion. Also, you could use a buck converter, that's what I did.