I bought a set back in 2008/09. At the time I was using a Mopar Performance .533 hydraulic cam, but later switch to a .590 solid flat tappet. I replaced the 7 degree locks with 10 degree and bolted them on my engine. Engine was a drag only and shifted at 6000, went thru the traps at 6400. Ran them up until 2016 when I needed to freshen the motor. Did end up having 2 broken inner springs. After putting new rings and bearings in the shortblock and having the heads hand ported, new valve springs and valve job the car picked up .05 in the 1/4. 3150lb car ran 10.80-11.00s. I have since bought a set of Trick Flow 240 and picked up solid 2 tenths (I actually went to a smaller cam and smaller header) so they may be even worth more E.T. The 440 source heads are perfect for stock looking and street or mild street/strip cars. Very good buy for the buck and I'd definitely wouldn't mess with steel heads for the price of a stealth head.