hi @oldbuzzard the short answer is no, that part number won't fit a 3-cylinder. But here's the kicker, the 1835C didn't come with a 3-cylinder engine anyway!
It used a Continental L-134, which is a 4-cylinder. You should be looking for a ring set for that engine.
The '858' number you have is more common for other Continental models, so you need to be careful with the exact part number. I'd try to find a parts manual for your specific skid steer's serial number to be 100% sure
@oldbuzzard Interesting, thanks for clarifying. If your manual says 3-cylinder, definitely double-check the piston ring specs for that exact engine before ordering.