Suntour has endless variations of front and rear derailleurs that will handle a triple set up. I have an "XCD" on my Puch touring bike that works very well on my Specialized triple crank. The same bike has an "X-1" rear derailleur that works perfectlly, so much so that I was truly impressed. It is Accushift compatible and with the correct 7 speed shift levers (I'm using Superbe Pro down tube levers but there are nice 6 or 7 barcons still available) it has hard positive clicks that are chunkier but just as good as modern Shimano indexing.

But for your front derailleur I think the XCD, the XC9000, the Cyclone 7000 would work. There are way more variations than this if you've ever seen some of the old charts listing all the SunTour derailleurs for different applications from this era. I would probably avoid the XC Pro front derailleur unless you are using a mountain compact triple as these were called "microdrive" and the curvature of the cage is designed to handle a max big ring of 44 or 46 teeth, so its gonna rub if you use a road triple with a 52 or 53 big chainring. If you don't mind mixing and matching components I would also recommend the 9 speed era Shimano Ultegra triple front derailleur the "6503" - its absolutely stiff, quick and accurate through a triple crank and easy to trim. It has a matte finish to the chrome that to me, sort of grabs the chain and makes quick shifting and trimming a little more tactile and a "no-brainer" so to speak.

For the rear derailleur if you wish to stay with SunTour I would encourage you to get a GT caged Accushift compatible model such as the X-1, XC7000, XC9000 or XCPro in any of the cage variants of short, medium or long cage. You could go with older Cyclone GT or Superbe touring type but these are not going to be index ready out of the box.

Good luck with your project bike!