New subwoofer/stock JBL box

Ok you audio guru's:

My stock JBL sub is shot and I have an 8" JL Audio sub to replace it with. The JL sub will fit into the stock box with little modification to the box.

Question:

Which is the best way to mount the sub:

like the original, facing upward so it fires off the back window? If so, do I cut out the top to allow the entire sub to be showing?

or

cut a hole in the bottom of the facotry box so the sub fires down at the floor? (The original hole on the top of the factory box could act as a port, I think.)

There is a wad of packing stuff inside the sub box. Should I replace this with better material or just leave it out?

The rest of the system is working fine (for now) so until it craps out, it stays.

Thanks,

Mark
'93 SC

dont take the wad of packing out

Dont remove the packing, what it does is slow the sound waves and make the sub act like its in a larger box-makes i sound much nicer-as for ports, there designed to be made to certain specs, so makeing your own may not work the greatese-you def. dont want a huge port like the size of th speaker. good luck, mike.