I'm sure if worse came to worse you could find non-Torx screws to fit those specifications.
Also, if you are taking apart Macs, be careful not to confuse the Torx screws that hold the chassis and CRT in the computer with the case screws. Some later model Classic IIs actually had gold-colored screws for the chassis and CRT to prevent confusion. The silver screws look nearly identical except the chassis/CRT ones are shorter. If you use these in the case it won't fit together, and if you use the case ones for the CRT, you'll get what resembles a huge pimple on the other end of the case...