Yes.
You can use regular-grade, 89-octane gas for all Mustang engines except High Performance (HiPo) models. If the engine "pings" under load (makes a rattling sound, like marbels in a can), check your ignition timing before upgrading to more expensive gas.
Also, don't bother with lead additives.
While older engines (including those built during the vintage Mustange era) were designed for leaded gas, they work just fine with today's unleaded.
And if the engine has had valves reconditioned at any time after the mid-1980s, it probably has hardened valve seats, which are designed for unleaded gas.
submitted by a65ragtop