Portable drive not really a good idea
You'll create bootsector problems doing a portable drive install. You would be better off doing a two way permanent hard drive install by shrinking a partition to allow room and then using the portable as data and back up space. IPC 10.5.6 ppf 4 or 5 seems to be a complete one that has good compatibility. You do not give much in the way of details about the planned machine you are going to use - so visit HCL 10.5.6 - OSx86 to see issues of installs.
If you use a portable drive - don't expect too much easy fast help if problems arise - and after all this support is free only for those who want to take time to answer a question. if you dig yourself in deep with a big problem - expect silence or guess work only.