Octane requirements

I just bought a Duster. (Insert happy dance here.) It seems to be a stock Magnum long-block with a Holley QF carb on an RPM Air Gap intake, headers, Hughes cam kit with 1418ALN-10 cam and roller rockers, about 9:1 compression, iron Magnum heads. Considering this, will this run on 89 octane? Or even 87?