Squareback vs round back alternator?

I used a square back on my 71 Polara in my avatar. It's a 440 with AC. The square part of the alternator is tight up against the head, I had to space it out a bit. I got an original round back with the 2 fields rebuilt, but haven't yet installed it. The guy at the rebuild shop said it shouldn't really be a problem- I have 15,000 miles on it that way. I was concerned that the heat transfer from the head would boil the grease out of the rear alt bearing.