Kerby,
I know, I know, I know you want me to tell you a grade level for each guide!

But, I can honestly say, after 11 years of teaching public school, that students within the same grade are all over the board in their abilities, so the grade level markings become all but useless!
This is why there's a range of ages listed for each program. Placement matters (and varies) for same-age kiddos depending on their personality, their previous learning experiences and subject coverage, the style of the teacher (and whether you like to teach the plans "as is" or whether you are a "tweaker" and an "adder"), and also varies depending on whether you are using our language arts and math recommendations or not.
For example, in my own family I used "Little Hands to Heaven" with my second son when he was 4 turning 5. He knew most of it, sailed through it, and went right on to "Little Hearts...". He is on the upper age range of each of our guides. Now, my third son started "Little Hands..." when he just turned 3, and we took 2 years to go through it. He is doing "Little Hearts..." slowly right now, as he had just turned 5 when we started it. He is on the youngest end of our programs. Yet, our guides are working well for both of them!
There will be 4 more guides after "Preparing..." to cover the 4 year history cycle. That does give you one year of wiggle room if you're on the young end of our programs, and the better chance of finishing the history cycle (or at least going further through it) if you're on the upper end of our programs.
I know that isn't the clarity you're looking for, but it is the truth!
Blessings,
Carrie