The GenI and II car's head units had transflective LCD displays that were easily readable in direct light. However, it was not a standard Chrysler head unit, rather it was a slightly modified Alpine aftermarket head. The SRT/10 made the switch to the standard DCX corporate head unit, which uses a VFD display. Which, unfortunately, tend to wash out in direct sunlight. Not much you can do about it.
Sigh. Doubtful that an aftermarket would provide decent fit to the dash so we may just have to live with it.
there are some install kits which conform to the opening in the IP and mount a single-DIN aftermarket head unit. They usually don't look too bad. Though there are two problems:
1) aftermarket stereos usually have EL displays, which still wash out in sunlight, and
2) the sound system's EQ curves are stored in the factory head unit. If you switch to an aftermarket head unit, you lose the equalization and it's likely to sound worse.