I maintained 8 M1's for our club CMP rifle program for a lot of years. We completely wore out 3 rifle barrels during that time frame, having fired between 6000 & 7000 rounds through each of these three rifles. During that time, I replaced one or two broken firing pins, a couple of op-rod springs & several broken extractors. I might have replaced an ejector spring, but can't remember doing so. Never replaced a clip latch or clip latch spring.
By far, the most common failure was worn follower arms/follower arm pins. This will cause clip ejection on the 7th round and in severe cases can eject clip on 6th round (that is eject clip and one or two unfired rounds).
If I were to put together a spare parts kit for a Garand, it would include a firing pin, extractor, ejector & spring, op-rod spring, follower arm, follower arm pin.
Firing pin is the most likely to break and put the rifle out of commission.
Regards,
hps