I use Ubuntu on a Dell D630 with a 1440x900 resolution. That is clearly not 4:3, but 16:10.
However, I also use Oracle Virtualbox on the same laptop and also have issues in setting the desired resolution for new Ubuntu versions and ChromeOS.
Why use it in a VM?? If you don't want to change your harddrive, use a live-CD. That gets much closer to the real experience.
I use a dual-boot installation since I have applications that are not available for Ubuntu (or any Linux flavor for that matter) and also do not run in WINE.