I had no idea that Ford made a ’63 Hi-Po Fairlane. A hi po 289 the 4 door... unusual combo, but, I guess you could order about any combo of trim lines and engines. If you'd buy it, they'd sell it. But only 2 were made. Only this one survived

The Challenger 221-cid and 260-cid V-8s returned as options for 1963, the only news was the debut of the High Performance 289-4V engine (aka Hi-Po 289). 

This engine was based up on the small-block V-8s that had debuted in the Fairlane line in 1962, but besides being punched out to a larger displacement, it also had cast-iron headers, solid lifters, a nodular iron crankshaft, high-performance connecting rods, a wider harmonic dampener, a dual-point ignition system, Autolite 4100 series four-barrel carburetor, a hot camshaft and screw-in rocker-arm studs, among other performance goodies. These tricks brought the Hi-Po 289-cid V-8’s performance potential to 271 hp

only one other four-door sedan with this engine had been produced in 1963, but it had been scrapped before it could be saved — likely for its valuable engine and drivetrain. 

This leaves this Hi-Po 289 Fairlane 500 as the sole surviving K-code four-door.

the Hi-Po 289 was the same engine supplied to Carroll Shelby for use in Cobras

https://www.oldcarsweekly.com/car-of-the-week-1963-ford-fairlaine-hi-po-four-door

I did NOT know the Hi Po 289 was a solid lifter cast iron header engine!