So... Apple didn't sell a configuration of the 4400 with the 604 in it, but there were clones that used the "Tanzania" architecture that did. here's an example. And here's another one. (And there's more...) I'm pretty sure at least some of those clones used exactly the same motherboard as the 4400, just with a different combination of components populated... and, aha!:

They're unfortunately tiny images, but here's a Power Mac 4400 motherboard side-by-side with one from a Motorola StarMax 4000/200, which came with a 604e. Exactly the same thing with a different beard and moustache. Here's a better picture; this board has a slightly different part number silkscreened on it but it's definitely (almost) the same thing, down to the "APPLE COMPUTER INC."