Here's what people wrote when I asked about my 99. Although, they come with flat slides, not round ones. The 98 should be very similar.
'99 Arctic Cat snowmobiles
Improperly manufactured clutch could break apart; flying fragments could cause injury.
Models: 11,507 snowmobiles of these models: P/S 700, P/S 700LE, Thundercat, Z 370, Z 370 International, Z 440, Z 440 Sno-Pro, ZL 500 EFI, ZR 500 EFI, ZR 600 LB, ZR 660, ZR 700, ZR Sno-Pro, and ZRT 800.
What to do: Have dealer replace clutch if necessary.
Anyways the rear is 13.5" total with something like 10" vertical. The front in AWS V with 8.2" of travel with a 41"ski stance. Dry weight is about 485. Gas tank is 10.5, oil is 4qts, and engine cc's are 599. You have 38mm round slide carbs and 78mmx62.7mm borexstroke. I would send your shocks out to be rebuilt by Goodwin Performance in Zion IL or Carver Performance. The cost should be about $100 for all 4.
I also remembered that the 98-99 600 had a smaller crank and crankcase than the 2000 on 600's. Some of these twisted and broke with heavy mods but I would think you would be fine.
These had about 100hp. They have shocks that usually need to be rebuilt every 1500-2000 miles. Take nicely to clutch changes. Some problems but seem to be hit or miss. Shocks and springs are stiffer than a ZL. Jet it, Clutch it, 96 pics, and 6" carbides.