Height on those tires are only about 1/2" different in total diameter. The main difference is the width, the 235 is about 3/4" (20mm) wider than the 215. The 215/85 tire, probably, is a higher load capacity.
The dealer or a tire shop should be able to look up what came stock on your truck, or go look at another truck of the same year and model.
1993 K3500 - Peninsular 18:1 engine, marine injectors, high capacity cooling, AL Core Radiator, 3" DP and 4" exhaust, ISSPRO Gauges, Girdle, AMSOIL Dual Oil Filter System, 1997 Air Filter(trashed the K&N), 395K on Body, 165k on engine.
1997 GMC Savana - 6.5 TD
1966 CJ5 - V6 Gas - highly modified
1967 Jeepster - Stock
1986 Jeep CJ7 - Stock
1993 Grand Cherokee - 6.2 diesel
2007 Grand Cherokee - 3.0 diesel