It's definitely no piece of cake getting them in there. I believe the collector is 3". I put my car in storage last weekend, so I can't tell you for sure. Check out some of the V6 Mustang websites for good advice on which headers to buy. The SC engine and the stock 3.8 Mustang are identical as far as header fitment goes. Even the SC dipstick will still fit. I wouldn't spend the extra money for Kooks headers, unless they come with a big sticker to put on the back window. They seem to be a waste of money, unless you have a situation where no other options will fit. Fortunately for you, there are lots of options. When you buy your headers, make sure to get the best header gasket you can find. Also, pick up some locking fasteners for them. Mine would back out every 100 miles, and the exhaust would start leaking. Summit has Stage 8 Locking fasteners for around 80 bucks if I remember. Then, if you still have money in your wallet, spring for the ceramic coating.