The original version of this engine was used in the 1969 and 1970 Boss 302 Mustangs and Cougar Eliminators and was constructed by attaching heads designed for the planned 351 Cleveland (which debuted the following year) to a Ford small block.

Available only in the Boss 302 Mustang, it derived from a line that traced to the Ford 289 HiPo engine, not a stock "Windsor" 302.

It had its own block, based on a unique thin-wall, high nickel content nodular iron casting, with performance upgrades that included solid lifters, much stronger 4-bolt rather than 2-bolt main crankshaft bearings, threaded rather than compression freeze plugs, and custom-fitted canted valve heads that gave it larger valves than on most engines more than a third greater in displacement.

The engine also had a distinct harmonic balancer, crankcase windage tray, bigger diameter alternator pulley (from the 289 HiPo), and bigger diameter power steering pulley, all to accommodate a higher-revving engine than the standard 302.

They are capable of handling up to ~8k RPM, aided by a spot face for 3⁄8 in (9.5 mm) bolts with a unique football-shaped head (vs 5/16 for standard small blocks), and beefier cap.

Because of the pent-roof design of the heads, the Boss also had forged pop-up pistons to achieve the desired 10.5:1 compression ratio.

Ignition was handled by a dual point distributor firing unique small-diameter 14 mm (0.6 in) AF 32 Autolite spark plugs necessary to fit within the tight confines of the combustion chamber alongside the very large valves.

[7] In 2007, Ford Racing began marketing new crate engines using the "Boss 302" moniker with displacements between 302 to 360 cu in (4.95 to 5.9 L) that are rated from 340 to 360 hp (254 to 268 kW).