The 413 is the better and stronger engine than the 410. One of the 410 weak points is a very small bore oil return pipe from the head which can be blocked if oil changes are neglected. Valve guides can wear in the heads; this is usually obvious if there is puffing from the oil filler cap with the engine running, or the breather to the air filter box has been disconnected.
Fuel lift pump also spring an internal leak and pump out the engine oil thru a breather hole on the bottom.
Look out for rust in the rear floor, front footwells, the front inner wings and aroung the headlights.
Otherwise they are cheap and robust off roading.