350/350 vs 350/370. whats the difference?

[KLAB]

I know there was the 350/350hp LT1 and the 350/370hp LT1. But what was the 20hp difference there? My step dad has a 350/350 4 bolt 1970 LT1 block in his 68 corvette with domed pistons and the "350hp" solid lifter cam. There is an empty old box in my shed that has "370 cam" written on it in sharpie. My step dad doesn't remember much, but he thinks he put the cam in one of the engines we have laying around. Are the 370hp and 350hp cams different? I couldn't dig up anything on this maybe Dawg will bestow his knowledge.