Yeah, I would base it off of a real car. I just did a quick measure of mine and the bottoms of the pedals (like the actual surface your foot goes on, not the whole assembly) is sitting 6" from the floor of my rig. As for the angle, mine are sitting at roughly 35 degrees, although this has to change depending on how high your seat is in relation to the pedals.
And one note about the 6", I play in socks, and that is too low for me to use with shoes on, so how they'll be used is something to consider as well. My rig's floor is also flat, but most cars would have a slightly angled floor which could affect the comfortable height of the pedals. Good luck!