I have a 00 XLS 4.0L with a tt and shkls and going to add a 3" body lift. Can I fit 33's in a 12.5 width and go with 15x8's or 15x10's?? Or do i need to go with 11.5 in width on 15x8's this I know will fit. For over a grand this is potentially a big mistake to get the wrong ones.

With either choice you'll have to trim. The 12.50s will fit, but use 15x8 rims for better results.

They'll fit but they will rub. No serious damage will occur with 5" of lift though, just be ready to trim.