Manufacturer functional interchange
Boston Gear 862B/863B appears in the same manufacturer-published cross-reference row as David Brown M062(3)BRN at Match installed ratio/application · Boston 800 size 860 · Foot mounted.
Boston Gear publishes 862B/863B for 800 Series size 860 in the foot mounted column of its in-line helical interchange guide. Boston states the 800 Series is designed to be functionally interchangeable with listed drives while requiring verification of ratings and dimensions.
The manufacturer describes the target family as functionally interchangeable with the listed competitor model or configuration.
David Brown M062(3)BRN and Boston Gear 862B/863B are tied by the published source at Match installed ratio/application · Boston 800 size 860 · Foot mounted.
The source still requires ratings, dimensions, ratio, fit, and application conditions to be checked before ordering.