Do you need 8 inch?
Ive ridden in some cars that have 5 inch factory speakers in the doors and or panels that sounded really nice.
The VW monsoon radios are tremendous.
Also, have you considered the seats that have the small speakers inthe headrests?
Keep the ideas coming, its not easy to get a nice stereo in an EB.
Should be able to get some in the kick panels, with the enclosures actually outside the truck, under the fender.
You could just do like alot of the people do in the 'hood Ive been working in...
mount loudspeakers in front of the radiator and drive around making everyone listen to your crappy music. Which is better I guess than the bass music that rattles the trunk lid.