can i convert my stratocaster from SSH to SSS pickups? correct me if im wrong but do i change the pickguard and remove the bridge humbucker and put in a new pick guard with SSS pickups?
Yup, you nailed pretty much what needs to be done.
Unless it also has a locking trem and you want the guitar to look (and sound) like a real classic strat. A cream MIJ strat should make for a good looking and great sounding classic strat. Go for it, man.
I never did understand why Fender, or anyone for that matter, would want to have humbuckers on a strat (can you say h-e-r-e-s-y?). You want humbuckers, there are better guitars for that rather than the strat.