In making a pudding, can you replace yolks with whole eggs?
You certainly can replace the yolks with whole eggs but you wouldn't do one-to-one as that would give you too much volume. The average egg has more volume in whites than in yolks (it's about 60% white and 30% yolk) so you'd want to use three whole eggs, not six.

Unfortunately, whites may give your pudding a texture that you won't like - one site calls it "jellyish" (meaning like gelatin), so you may want to use a combination of whole eggs and yolks alone, say, two whole eggs and two yolks. This would be about equivalent to using six yolks but will reduce the gumminess.