I'd say it's a maybe. Your Shimano levers are later production, by the time they went to SIS/indexed they were spec'd to mount on standard dt bosses, not the earlier Shimano-only "A" type.

The problem is I don't remember what lives under the Suntour Power Shifters, whether there's some kind of shoulder build into the clamp for the shifter. If not, and removing the lever just leaves you a flat surface with a standard boss-type mount, you're approaching good.

But only approaching good because your Shimano levers use a curved/radiused shift lever boss cover, the silver piece that goes between the lever and the frame, but what you'll need are flat ones to fit the clamp. You can buy 'em, maybe $12-$16/pr? They're usually stock on Shimano bar-cons.

So it's a kinda/maybe/who-knows?