It appears that all but one lifter in this motor was replaced with a different type. The check ball is replaced with a plate and a small spring.
This is what I would say is an original which I only have one; http://s1142.photobucket.com/user/52_Ton/media/Motor/IMG_2129.jpg.html?sort=3&o=2
This is what the other eleven lifters look like;
http://s1142.photobucket.com/user/52_Ton/media/Motor/IMG_2131.jpg.html?sort=3&o=0
Are these valves adequate for this motor and should I find one more to replace the odd one so they are all the same?

Mark

1952 GMC 9430 one ton pickup, a work in progress

1952 1-ton pictures on Photobucket