Yeah probably more work than it's worth to make the magnum kit adapt, you'll have to cut off the header, buy or make a flange, cut and weld the flange on the header and weld the header back on. The proma also needs the 3rd mounting point that attaches to a head stud, so it's extra tricky to line up.
TBH the magnum stock exhaust is already pretty good, it's not a chamber pipe but it does have really good low end. If you can bump the compression a bit, 15 bing, and tune the clutch it makes a really solid 35 mph bike with good torque. Megan bandit had that setup on an orange pinto back in like 2006 that absolutely murdered hills and got up to 40 with a quickness