Try this they have all the parts you will need. www.latemodelrestoration.com
According to my Chilton's Auto Repair Manual : A 1991 Ford Mustang has a ( 15.4 U.S. gallon gas tank )
Yes the front seats from a 89 mustang v6 will fit in a 91 mustang, the tracks are the same.
Yes.
green.
You don't repair a muffler, you REPLACE it.
Rear of the engine - front of the transmission
In the fuel tank
There are many different kinds of camaros and mustang depending on the engine what one is faster
Get a replacement 'retainer clip' from your dealership for under $3. You might find the pieces of the old one in the bottom of your door. It will clip onto that rod, then snap into the hole on the latch.
2 words for you, Repair Shop! There are a couple of sites that give info on those pesky door repairs. No need to pay a bundle to some repair shop, if you know a little about nuts and bolts. Do a google search on: Buick window repair. Lot's of replies 'cause there's lots of problems.
Yes.
... what about them?