Plymouth Factory Service Manuals... something odd.

mvh said
Yes, of course. The 67 covers Valiant, Satellite, Fury but not Barracuda. The 68 covers all 4, so the body section should have more pages, right? In terms of engines and options, I am not sure which year would cover more items. They added the 340 in 1968, so that's one more engine... they dropped the 273 but added the 318 — that's a wash. I should actually look at the books, but I'm supposed to be working...<LOL>

There's a lot of overlap. All small blocks are covered in the same section, with somewhat sparse notes for the differences. Even the 440-6 only has a special section on the triple carbs, and the engine section you have to dig to find any of the special stuff. And they don't mention stuff like part numbers, or EG differences in rods, etc.