Most of my radio customers are using the outboard e body speakers from turnswitch.com
The main problem you might find is due to the small size of those speakers , they will have their limits as far as how much sound you are going to get out of them , and how much power you can put to them .
What I recommend when we do the 180 watt conversions on E body radios, is they run two in the back in the package tray , and two in the dash, either the small outboards, or the "two in one" 4x10 center, and adjust the radios fade where about 70 % goes to the bigger, more powerful rear speakers and about 30% to the front speakers .
Greg