we are waiting for an answer to an ongoing thread to find out the pipe diametre of the 4.4.The pipe diametre of the 4.6is is 57mm and the 4.8 should be the same!If the pipe diametre of the 4.4 is the same(i doubt it!),then it should be a straight bolt on!
You cannot just have the 4.6/4.8 tips ,you have to buy the exhaust system that goes from the oval tips to the middle resonators.Alternatively,if all you are after are the tips,you can just get after market oval tips(non oem),See an article in this site.............