Open the txd file with the latest version of txd workshop, click VCXBOX at the bottom right selection box, then click save. Images in the txd should be no more than 512*512 in size. Then open the gta3. img with image editor 2.0, then replace the file of your car or whatever with the modded one that you downloaded and converted to VCXBOX type. Then click Commands, Rebuild Archive. Then FTP it to San Andreas\:Models\
Then delete your 'box's E:Cache folder, and delete all files from in your X, Y, & Z cache partitions (you will need to do this everytime before loading GTA San Andreas). UnleashX does it but there's an evo-x 3935 .ini extension that adds the "Clear Cache" feature to the menu. Also do only one or two mods at a time and then test them because otherwise you'll spend all day editing the img and textures to find that it crashes and you don't know which of the 35+ mods is causing it. Editing the handling files and similar files can easily cause it to crash.