What A-arms do I have?

[cptstickfigure]

Back when I bought my '64, the previous owner threw in a bed full of parts that he'd been collecting for future upgrades. I've got A-arms and spindles for a disk brake swap that are supposed to be 1972, but I know better than to take anybody's word on that sort of thing. I didn't think much of it until I started looking for rebuild parts the other day and noticed that '72 A-arms use different parts than '73 up. Is there any convenient way (casting numbers or something) that I could check what I have or am I better off trading to a junkyard for a known year?