Well that sucks! I have never seen one without a high range. Learn something every day. Son in Law's '90 trail boss has a high range, but that one is a 2 stroke also. My buddies 2000 500 Scrambler 2X4 just has F and R on the shifter. Sport machine to be sure but designed for trail, not work so much. Not sure what the difference is between the Magnum and a Sportsman. It would seem then that the Magnums were designed as a work machine only.
There was a Sportsman 4X4 in 1995. It had chain drive and was used in the Sportsman, Explorer and 6X6 up Through 1997. Also a Scrambler 4X4 in 1995 with a chain drive.
Might be a few possibilities there for a transmission swap. That would be the only way I can think of to get the high range. Just throwing ideas out there for you. Good luck with the project!