No, you should not substitute a 215/60R15 tire for a 215/70R15 tire on a 2001 Dodge Caravan. The difference in the sidewall height (the "70" vs "60") is significant. The 60-series tire will have a smaller overall diameter, affecting your speedometer accuracy (it will read slower than you're actually going), your odometer accuracy, and potentially your transmission's performance. It could also negatively impact your handling and ride quality.
While a slight difference might be acceptable, this is a larger enough change to cause problems. Always stick to the tire size recommended by the manufacturer for your vehicle. Check your owner's manual or the sticker on your driver's side doorjamb for the correct tire size.
