Great info man. When you heat the enclosure to fit the magnet do you think it will get into the window when it rolls down? I betting that if you can keep that enclose and fill the hole those 8's will have a nice kick to them from 70hz to around 120hz the component set should pick up from there nicely. I have the hybrid audio 6.5 and tweeters, these 6.5 are beatly and have considered replacing the 8 with the 6.5 all together then making a plate for a set of 4 inch and the tweet. If the 8 works and sounds good, I would like to run them. I think the phrase is bigger is better right. If price wasn't the problem would you go with a different sub like the slim subs from Rockford, JL doesn't make a slim 8 according to my dealer. I'd like to get as much info as possible. Keep me posted ace I'm intrigued.
Be advised these 8" speakers are woofers, NOT SUBS. Here's the thread where I was going down the same road, of what to do with 8" speakers in these doors. IMHO, Ford had to use the lowest cost option possible to use subwoofers - at 1.2 ohms no less! to squeeze out any kind of bass response for their Shaker stereos.
Now here comes the consumer, ready to rock the house with high powered amps and quality speakers. Putting 2 sub woofers right up front in your doors could easily end up being overkill, so I took the advice given in the thread below, and chose the woofers instead for the doors. I'll build my own sub box for the trunk. I want powerful, full ranged, balanced sound, not a mobile boom box. Anyone measure the lower speaker cutout diameter? - The Mustang Source - Ford Mustang Forums