The U-shaped retainers inside 5.0 roller lifters can get lost during cleaning. Sprong!
I thought I have to scrounge or buy a new lifter set rather than just clean my present set.
I took a chance and ordered Crower Cams 66000SR-16 "snap ring for hydraulic lifter" (16 snap rings) and bingo! Less than $20 (15 something as I recall).
Pics below:
