Source for RV interior specs?

Your most reliable source would be a trip through a sales lot(s) with a tape measure. RV's are notorably variable in build dimensions, even between two rigs identical going down the production line together. They will always come out different, not where you can see, but in the details.

Look through some rigs and measure the ones you like .. that will give you a jumping off point for any mods you might like. Keep in mind the rig you buy might not favor what you want, but you'll have a ton of great ideas.

I don't know of any manufacturer that makes those type of specs public. Each RV built tends to be somewhat unique to meet specific design and price points. Dinette seats for example, can be used to enclose various electrical equipment, a water heater, a furnace, etc., depending on the floor plan and wiring/plumbing layouts. Ideally for your purposes, they would only be used for storage, as some are. If you're thinking of extending the kitchen counter into the dinette space, then of course you would first have to choose a unit with a suitable floor plan that has the kitchen counter and dinette on the same side. You would probably be better served to wait until you're closer to purchase time and start looking at suitable candidates to buy with your potential changes in mind. The likelihood of finding one that's exactly what you envisioned ahead of time are pretty slim, so be prepared to be flexible.

Folks have been asking for build plans, wiring plans, plumbing details, stud information, construction details on these forums before I ever knew RV.net existed and no one has ever been able to break through the manufacturers deep hidden secrets. Keeping gold at Fort Knox is easier to access than the building diagrams and schematics from an RV manufacturer.

As stated above, your best option is to simply narrow down the camper you are interested in and then out with a tape measure. See if it's do-able. That is probably the only way to get the information.

Thanks for the quick responses, guys! I was hoping for better news. As a former engineer, I'm a bit annoyed by the lack of standardization and product info. But as a crafts woman I guess I do have an appreciation for one-of-a-kind objects! I'll just have to keep my designs and my budget in the guess-timate stage for now.
- Eli

“I'm keeping the dream alive by designing the modifications...”

You want to modify an RV you have not yet selected? A “C” with a lunch counter? Interesting.

Nothing wrong with being a railroad engineer. I’m from a RR family!

“I'm a bit annoyed by the lack of standardization...”

And I’m happy behond smiling that everything ISN’T “standardized.”

can you go online and fine all the info about track homes ?

counter heights pluming routing etc..

RVs are just homes on wheels

counter height only varies a little bit

But dinettes vary a lot, the shorter the RV the more likely something is stuff under the dinette, instead of open storage space

you can find brochures, floor plan layouts, on lots of models

but you won't find measurements detailing size (except for maybe the bed)
some tell you the size of the sofa bed, or dinette sleeping area

none tell you where they place the water heater, the furnace, the converter, the fuse box, circuit breakers, plumbing

I like your way of thinking!
(Almost) Half the fun of owning an RV is improving them. I'm spending my winter doing upgrades, modifications and organizing.

Winnebago Resources, have diagrams and specs on virtually all their models built.

Ken