Frame diagram inconsistencies

[RacerX]

There are a few frame diagrams floating around that have been created by "someone"
The origin of the diagrams appears to be from of an aftermarket frame dimensions book
sold to body shops in the 70s, but not 100% sure.   

They are not the ones from the factory service manuals.

They are not consistent in ways that do not seems to make sense...

First, the 1970 barracuda diagram in the Reference Material section on here is wrong...   
dimension "D" is NOT 15 7/16, it is  "something else."     What that "something else" truly is?   
I cannot find a corrected diagram for '70 Barracuda, but the dimension given in the 1970
Challenger for "D" is 18 1/4 and probably holds true for Barracuda.    A notation of some sort
should probably be made in the posting containing that diagram lest someone trust the data
to be correct.   

All the other dimensions given on the 70 Barracuda and 70 Challenger diagrams are the same
except for the ones affected by the two inch wheelbase difference of the two cars.

Now enter the 1973 Challenger diagram...   a fair number of differences

A is different by 1/16... not significant enough to worry about

D is different by 9/16... why would this be?    That is over 1/2 an inch, and is a big enough
difference that some parts would not interchange from other year e-bodies.   Is this an error?   
How could the end of the 73 frame rail be 9/16 lower than the 70 frame rail without throwing
all of the other sheet metal (trunk floor, wheel housings, rear seat pan, etc) into chaos?
Maybe the reference vehicle they used for the measurements was hit hard in the ass end...   

K...  wtf?    how can this measurement be 4 3/8 different?   Should be exactly the same...
Did they relocate the guide holes?   Seems silly as it would necessitate tooling changes
for no obvious reason.

Really not sure what to believe on these diagrams...  would like to think they are useful
because they are the only ones that show vertical dimensions from a datum.   The factory
diagrams do not show this.    However, I have serious doubts about the accuracy of any
of the information in these diagrams.

[torredcuda]

Ya, some of those dimensions make no sense - the rear spring eye to eye is the same the the rear frame rail is different, that can`t be. Where did you find these?

[torredcuda]

Found it - https://www.amazon.com/Bottom-View-Frame-Dimension-Charts/dp/B000ETUO1M

[Brads70]

Your right, good catch. Yes these are from aftermarket books sold to shops. I have used them from a local frame /collision shop. It was a spiral bound book, looked pretty old and well used lol.  Never paid attention to who made them though.  I used to be a tech inspector at a local circle track and we often borrowed/photocopied them for reference to see what/where the chassis were "altered" in the stock divisions.....

[RacerX]

Ya, some of those dimensions make no sense - the rear spring eye to eye is the same the the rear frame rail is different, that can`t be. Where did you find these?

Some of them are posted on this site...  they seem to pop up whenever someone talks about frame specs.
Googling turns up these same ones posted on other mopar sites, along with some b-body versions.

Due to the inconsistencies, I don't see much value in them unless someone has some theories on why
the data would vary so wildly...   I think this is just crap data, and anyone that paid real money for it in
1977 got took by Mr. Depew.

Although the mopar service manual diagrams are not without their own head scratchers...     such as
diagonal spring mount measurement 76.04 consistent across all years barracuda and challenger, but
spring mount to spring mount on the same side varying by ~3/8 inch.    70 - 56.5, 71-4 56.88.  If
you change this measurement, the 76.04 would have to change also, but it doesn't.

Did they really move the k-frame ~1 1/2 inches aft for 1974?    It is possible, but I've never heard of
74 models having such a change...