The OEM Clutches are very good. I have seen some of the A/M ones scatter in the old 80's toyota pickups as they were all standard until around 1987 ( I think)

If the clutch isn't slipping, I wouldn't change it. However, when you do. Be sure to make sure they flywheel isn't blued or any cracks on its surface. If it does, be sure to replace it as well. When I do clutches, I change the pressure plate, throw out bearing, pilot bearing and clutch. If getting really higher mileage, I will change the real engine main as well.

When I use marlin crawlers, I am sure other folks out there use other clutches or even use the OEM clutches as well. :-)

This is why I chose the Marlin Crawlers kits:
All kits feature new parts. Each Kit Includes:

Heavy Duty 1,200 ft-lb Pressure Plate (stock pressure plate is 900ft-lb)
33% higher load rating than stock
Heavy Duty Metallic Clutch Disc
Japanese Release Bearing
Pilot Bearing
Alignment Tool

The rest of the parts I get OEM. This is just what I do. Hope it helps. :-)