I dremeled the box so the new sub would fit flush. There are 6 or so small vertical plastic extensions on the inside lip and an index piece at 12 o'clock just above the sub hole that have to be trimmed. Not much just a little, check fit as you go.
You need 6 extra screws as there are 12 holes...
Just finished the MB Quqrt install. Was able to go back with the original cover and trim ring, just a little dremel work to get sub to fit flush, very clean. I did use poly-fil.
The sound is a vast improvement, tighter and a good bass thump. It's a "no brainer" for $57.00 bucks.
I just finished doing this and I have to agree, best $57.00 spent in a long time. With a little dremel work I was able to put the original cover and trim ring back, it looks original. The dremel work was done to make the speaker fit flush.
You can use the original screws plus 6 extras and the...
Ford house, it fits and looks the best. Tascaford or one of the online dealers will have your year model and order from them.
Go to the Ford Mustang build site and it will be there somewhere, you can get a look at it.