Just a tip, be aware that different emblems are fitted to '77 and '78 models, even though they appear the same, the pins are different. '77 (GM #598834) has 3 pins that are plain studs, '78 (GM #549367) has 2 pins and one has a larger support off it so it won't fit in a standard hole. That, and the numbers, should be enough to check what it fits.
Ebay used lists them as the same piece which is an obvious assumption. Otherwise if you get stuck they are about $25 new repro.
Also, if you can get a good used set of wipers then go for it. There are repros now but the splines in the arms are very fine and not as robust as originally. I stripped a brand new one on it's first test, with window cleaner on screen, swapped back to used. It may have been an outside case, but still, the seller who was also the manufacturer didn't want to hear of it or any refund.
