the Ford 289 was a compact motor made for track racing. IT's a lightweight motor, and more importantly it has incredible potential for revs and installs.
You can install a Ford 289 almost bolt-in in an older Toyota RWD. The 289 IS a substantially different motor than the Ford 4.6 current motors. The block is the same, but only in terms of rotating assembly. I've seen mildly tuned 289s in 67 2+2's at Limerock doing 9000 rpm without breaking a sweat. I've also seen them in offroading trucks idling along at incredible torque.
Some clarifications:
The 1963.5 Mustang intro had an inline 6. 1965 fully introduced the 289 V8 with low 200's hp.
The high-po 289 was found in 1967 racing, and 1968 production as a K-Code.
Cobras also came with 289s. It's rare, but more common than some other Cobras. (Typical drop-in was the 302, 351, and it's more common than a 427 SO or the 351 AC/SC)
-> Steve
I haven't run through the fact checker yet, but this is just me talking. If you are interested, I suppose I could do a write up.
The mustang was debued in 1963 with a 271 HP 289 V8.