Got gas, ford sub wont fit, don't want to use heaps of spacers and have it sticking out the top... so who makes a shallow 8" sub. All I can find so far is blaupunkt and pioneer's 10" and 12" subs.

Pioneer definately do a shallow 8" sub woofer, we deal with them at work, and I rang them once and asked, it was very expensive. Earthquake SWS-8 is a good unit.
http://www.fordmods.com/forums/viewtopi ... highlight=
I've decided to keep mine now but.

You are right, pioneer does an 8", just found it. They dont show it on the site but it says they do em in this press release http://www.pioneer.com.au/insidepioneer ... less_space

does the parcel shelf vibrate to the s**t when installing a sub on it?

if u mean with the premium ford sub then no but if u r talkin bout a bigger better sub then i would assume u mite want some sound deadening

It would but would depend as said on how powerful a sub you install....the factory ones dont have to high an output hence vibrations are minimal....however going aftermarket and beefing it up, it would highly like some rattling is bound to happen....an mdf spacer, sound deadening or absorbing material would also assist even the extent of an old shirt/towel hidden underneath to absorb the vibration also assists...

The Pioneer on is a TS-SW841D. I bought one months ago from autobahn for $200. Expensive f**k!!

The idea was to conceal it as best as possible, so I went for 8'', realising after I got home that I had not been sold a free air sub. It sat in the spare room for months before I hooked it all up and put a 4mm thick ring of rubber between the sub and the shelf and nothing vibrated but the sub had to be turned down a far way to stop it distorting without a box. Had to turn the 6x9's down too much to hear the sub so went and grabbed a 12" and box the next day.

Depends what sound you are after. The 8" would only need a shallow box but getting it to fit around the gas tank will be the tricky bit. The sub is only 75mm deep, so the box wouldnt be that deep, it would just be fitting it somewhere.