Is this worth it? 1974 440

Junk?!

Not at all. If you look at the 440 source website, they even prefer some of the later blocks because they have extra webbing, which adds strength. See here...http://www.440source.com/blockinfo.htm

The motor home part of the equation might be an issue though, depending on which heads it has. Some had motor-home specific heads, which you won't be able to use. Others just have regular car heads, so you'll want to check the casting #'s. If you've already got a set of 906's I think you'll be fine, but I'm not a big block expert so you may want to make sure the head change is all you'll need to do.