Today, if you buy Honda's own cam chain you get the heavy-duty version that is known as the '-410-' type (those being the 3 middle part numbers), which came out in the 750F2/F3. It has HD (thicker) pins, extra side clearance for the rollers (for improved internal oiling) and hardened side plates. They have subbed over the earlier ones to this number and offer just this chain, as it also fits the 350 twin engines. They show up once in a while as either NOS or new stock.