Dual Booting 9.0 and 9.1

I am currently running 9.0 and would like to install 9.1 on a partition now occupied by SCO Linux 4 (no comments please!) 9.0 is currently installed on /dev/sda5 I want to install 9.1 on /dev/sda3 but retain the ability to boot/access 9.0. How do I go about this? Thank you, Lucky Leavell