Many of Loeffler's designs feature a par 3 that is very similar to the #8 at Oakmont. The hole that is currently #11 (#7 orginally) at Hannastown is one. The original 9 holes has severe greens including a number of them that slope away from the player or to one side or the other. He also connected the putting green to what is now the 18th green (#9 orginally). But, in the case of Hannastown it is connected to the left side of the green instead of behind it at Oakmont. It is protected from play by a large oak tree. The bunkering is not as severe as Oakmont's and it is no where near as difficult.
Nemacolin Country Club also has a par 3 that is similar (#4), but since Tillinghast redid the course after Loeffler's original design, I'm not sure if it is Loeffler's work.
Loeffler was a partner in the architecture business with John McGlynn who was the superintendent at Oakmont before him. When McGlynn left, Loeffler (who had been Fownes Jr.'s caddie as a youngster) was hired as superintendent. They designed at least 20 courses in western PA, including: Alcoma, Beaver Valley, Brackenridge Heights, Chartiers, Churchill Valley, Hannastown, Hillcrest, Nemacolin, St. Jude, Wildwood, Oakmont East and Williams (in Weirton, WV.) Alcoma and Beaver Valley also have similar par 3s.