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Many MGP scooters come with HIC, which would work with oversized bars. If you're using SCS with your MGP fork, you'd need to go to HIC compression with an oversized clamp and slit in your bars OR full-size SCS (that can accomodate oversized bars) WITHOUT a slit in your bars.
You can't run HIC with standard diameter bars. It's impossible. They are the same diameter (or close), so one won't fit inside the other. However, IHC is a lot like HIC for standard diameter bars. You'll need a tapered IHC fork to do this.
I've never tried to put aluminum bars on a threaded fork, so I'm not sure how well it would hold. At the very least, you'd need an oversized clamp. I don't think I'd recommend aluminum bars on a threaded setup. You could upgrade to a threadless fork and threadless headset and then use SCS, IHC, or ICS with the aluminum bars, but that's a pretty expensive upgrade.