[1971WARBIRD]

another thing to think about, do you want any add ons?
with the 455's you could get A/C where you couldn't with the RA IV.
in 1970 they did a track test bettween a RA III 4speed stripped GTO and loaded RA 455 auto GTO. they were so happy at the end to say the RA III out ran 455, then they got into details;400 stripped, 4 speed, 3.90 gears-455 loaded as i remember about 300 or more pounds heavier, auto, 3.31 gears. the 400 did out run it a couple times, but the 455 won several as the 4speed had to leave the line perfectly to hook up, the 455, just put it in gear and drive away. when it did out run it, it was only by a few tenths, and as i remember, each hundred pounds is a tenth?????

having said all this, i would love either, and either is a great car with most things depending on tune and driver that day.