A The latest 7.5.1 WorldScript I requires updated script systems, and you should not install it unless you get these all from the same system. The Developer CD is currently the only source for these files. LaserWriter 8.3 is not compatible with older WorldScript I, because it requires 7.5.1.
The best solution is to perform a clean install of 7.5, install the 7.5.1 upgrade, install LaserWriter 8.3, and then test it. After confirming that this configuration works, install WorldScript I 7.5.1, the compatible script resources, and the power adaptor (if you have a PPC). It is best to get them all from the Developer CD (there is a 7.5 Arabic system with WS 7.5.1 on the CD).