a scale starting point

[Tk421reporting]

I dont know about you guys but my morning just started with one of my neighbors frantically screaming at the top of her lungs...now nothing...

aaaaany way haha, I'm new to this site, found it a few weeks back, just going through and getting my bearings and looking at some of every ones amazing builds.
what I want to start building is a chassis for an excavator in 1/14 but I'm not going to use a traditional straight long track. I want to have 4 independent D10-D11 dozer type tracks, and have a bit of suspension in them as they crawl along..still not 100% if i want the D10 tracks or just make it flat and have them pivot, just for simplicity sake.
somewhat like this https://www.youtube.com/watch?v=pBM8mjVDuHw

I plan on doing all the drawing in fusion 360 so I can easily print a 1/20ish abs model to start with.
the part that I'm currently stuck at is getting numbers and measurements to begin my drawing at, I've kinda been winging it but its put me at a few dead ends, so what I'm looking for is some way of getting measurements of what things are supposed to be scaled down to the size that I want.