Click pics for larger image.
Need more information

Has a 2 piece arm. Bottom bowl attaches with butterfly nut stud. 
 52AirCleaner.jpg (56277 bytes) 52aircleaner2.jpg (59124 bytes)
Photo:  John Kellestine
Similar to above but the arm can be removed from the bowl. 
aircleaner.jpg (58970 bytes)
nov54=> ~ mid56:
261 129 611
Arm now one piece
55cleaner.jpg (8232 bytes) wingutz.jpg (63815 bytes)
butwing1.jpg (45302 bytes)
~ mid56=>april1959:
261 129 611 A
Changed wingnut in favor of  a long bolt attached to bottom piece. bowl  now screws into upper arm.
57bottom.jpg (8721 bytes)
oilbath57.jpg (15901 bytes)
may1959-may60(bastard 40hp engine)
261 129 611 B
Added clamps to secure oil basin to arm. This was used on "bastard" motors only (late 59-early 60)
bastbath.jpg (14867 bytes)
261 129 611 C
Unknown. Need pic/info
261 129 611 D
Unknown. Need info
(note: I think the one shown in the pic has the wrong main arm on it. Should be a drivers side hanging arm, not a passenger side arm)

129.611D1 (1).JPG (205813 bytes) 129.611D1 (2).JPG (206405 bytes) 129.611D1 (3).JPG (207847 bytes) 129.611D1.jpg (208279 bytes)
261 129 613

Added air intake flapper. New engine tin piece with hole to accept Preheat tube  which comes up from the left side of the engine tin and goes into the bottom of the air cleaner. Also changed straps so that they hooked up higher.

Webmaster note: I
have one of these, same P/N....its identical, but the weird part is that it *doesn't* have a nozzle for the crankcase ventilation like the ones in the pictures. May have had parts miss matched at one time.......
60cleaner.jpg (24574 bytes)261 129 613.jpg (23544 bytes)
1963 1500cc option only
261 129 613B
crankcase ventilation hose now mounts to right of the flapper . Arm now composed of a rubber flex tube. 
  63onlycleaner2.jpg (82512 bytes) 211 129 613B-2.jpg (26247 bytes)
Oct1964 to 67??:  
261 129 613C
Unit now hangs to passenger side of engine compartment.
Hose mounts to left side of flapper. Preheat tube now goes into right side of engine tin
64cleaner.jpg (11927 bytes) 64andlatebrack.jpg (37498 bytes)
Late 60s still being researched...
261 129 613D?????????
Year(s) unknown.
Notice the crank breather tube mounts on the left like a right mount cleaner, yet the flapper snout is angled like a left mount cleaner??
613d.jpg (26759 bytes)
Bracket for air cleaner, attaches to the outer coil bolt and helps support the arm of the cleaner. Used for 60 and earlier cleaners until the cleaners started coming with a welded on bracket that attached to the truck body for support. This bracket attached to the cleaner arm, and to the coil bolts. cleanrbrack.jpg (25304 bytes) 
Anyone know the year difference between the bracket with the notch, and the one without?
Below is for early BUS ONLY, just so you know. You may see them advertised for *all* early buses. They will not fit in a truck engine compartment properly and are not korrect.
1952 only: T shaped tfilter.jpg (1723 bytes)
1953 only: Changed to a sort of "mushroom" style 53aircleaner.jpg (4209 bytes)
1954=>mid55: Lip added to keep debris from falling in. 54aircleaner.jpg (6515 bytes)
mid55 and on: Bus now same style as truck (diff p/n's).