have this stamping on sideof head R121209T does anyone know what it stands for

 

I assume this is from a 1967 motor? If so, that's the engine unit number. R = 425 cu in 4bbl motor. 121209 = sequential unit number (should match the Protect-O-Plate). Not sure about the "T" suffix, however. I've seen that on Toronado motors.

 

engine code is 390925E so I can assume someone put 425 heads on 400 or could it have come like that

 

As Joe suggested, RxxxxxxT = Toronado.




- Eric

 

It did not come from the factory like that. All 400 motors got engine unit numbers that started with the letter "V" that year. Of course, the same head castings were used on both motors, just the engine unit number was different.