I put the supports from an 03 zr onto my 99 which is the same tunnel as your 01 zr. Word of advice to get the rear susp. bolt holes to line up... grind off about an 1/8 of an inch of the support arms that rest on the foot rest of the running boards so they slide back enough. When you order them get the conventional style rivets instead of the ones they use from the factory(dont no what there called but they arent used much) you will need alot, not sure how many though. Also I would reccomend using a high strength air rivet gun to pull them tight, i work at a collision shop so I borrowed a bodyman`s. and get a buddy to help you as you need to force the supports to sit right while you rivet them.
Another option would be to use supports from a 99 snopro, I used those on my 01 zr, they are black so no need to paint and should bolt right on. One of the best things I did, I also put steel rods that I picked up at the hardware store in the roll to strengthen the boards some more. Some guys have found aluminum rods as well.
My fault the supports I got for mine were from a 99 ZR sno pro as well and they came in black, but be careful when you have the dealer order them as the first time my dealer screwed up and ordered the correct supports but in raw aluminum.