Newb questions

I'm having difficulties when trying to make multiple trims for a car... When I create a new trim for a vehicle which I want to appear in a later year (IE Base car comes out in 1972, but the Limited Trim comes out in 73) It resets the entire car group to 1973...
I also see this in the Engine creator (IE Engine family starts out in 1969 but for the limited car a turbo is added in 73, now all engines in the family are from 1973) am I doing something wrong? I scoured the manual and I can't understand why I'm not getting this right?
I'm also finding out later that you can't stratch the wheel arches after the body is finalized and that the display of the max size of the wheels/tires for the vehicle are not necessarily updating in real time. I had one car that said I could have up to 185 mm tires... but when I got to suspension, no matter how I adjusted the settings I couldn't get larger than 165... when I went back to the model created I saw that those were the default sizes for that model, and it telling me I could have 185 was wrong...
Lastly, though this relates more to the manual than anything. It says in the manual MTBS. Mean Time Between Service, as the durability score... It was measured in Km (Or Miles I'm sure for those that prefer that unit.) but in the steam version I'm playing I just get a score... and it's confusing... some scores seem to rank between 0-100 and other blow past 100 like it's not even there, so I don't know which are a percent and which are an arbitrary number... I would like very much to see my durability measured as service intervals... that's something I can relate to in real life.
Some love?
Truly,
Tex
I also see this in the Engine creator (IE Engine family starts out in 1969 but for the limited car a turbo is added in 73, now all engines in the family are from 1973) am I doing something wrong? I scoured the manual and I can't understand why I'm not getting this right?
I'm also finding out later that you can't stratch the wheel arches after the body is finalized and that the display of the max size of the wheels/tires for the vehicle are not necessarily updating in real time. I had one car that said I could have up to 185 mm tires... but when I got to suspension, no matter how I adjusted the settings I couldn't get larger than 165... when I went back to the model created I saw that those were the default sizes for that model, and it telling me I could have 185 was wrong...
Lastly, though this relates more to the manual than anything. It says in the manual MTBS. Mean Time Between Service, as the durability score... It was measured in Km (Or Miles I'm sure for those that prefer that unit.) but in the steam version I'm playing I just get a score... and it's confusing... some scores seem to rank between 0-100 and other blow past 100 like it's not even there, so I don't know which are a percent and which are an arbitrary number... I would like very much to see my durability measured as service intervals... that's something I can relate to in real life.
Some love?
Truly,
Tex