The GT 40 used 289s at first, then 427 OHV, not SOHC egines, as I recall. And, the Ferraris sucked up the 289 powered GT 40s, it took the big 427 to do the job. The SOHC engine was developed for NASCAR, cause the 426 Hemi was making more power than the 427 OHV engine in NASCAR trim. NASCAR mandated that each manufacturer had to produce a certain number of street versions of their NASCAR engines, Chrysler did, Ford didn't. That's why the 427 SOHC engine was outlawed in NASCAR. Ford then did some drag racing with the engine, but it was not suitable for street use. I heard they had issues with timing due to chain stretch, maybe someone else knows for sure. Anyway, Chrysler deserves alot of credit for detuning a racing engine for street use, and the Hemi is the engine everyone else compares to, and that's saying alot.