Howdy. Actually I work at an independant shop, so I work on all makes and models. My general experience is to always treat an engine as an interference engine. But, as a rule of thumb (not in all cases), if you don't have hydraulic lifters, you have an interference motor.
The problem of interference comes when installing the heads or changing out the timing belt/chain. Always, always, always line up the marks between the cam and the crank before setting the head down on the block. Make sure the head sits perfectly flat all the way around before installing your head bolts, otherwise you run the risk of bending the valves. Also, after I install a head, belt or chain I always turn the crank by hand, (very slowly, and leave the plugs out for feel) at least 4 revolutions to make sure the valves are not hitting the pistons.
Eventually this process will go very quickly and you can look at the position of the pistons and their mated pair and the position of the valves in the head and just know. However, if you always treat the engine as an interference engine you won't have any problems.
-Kevin
