x2. emphasis on ALL ASPECTS. I dont imagine you will pick up much MPG. but going from 7-9 up to 10-14 is pretty decent.
Say for example you are going for a drive and its a 600 mile round trip. Its al open highway, and your not hauling anything. and gas costs $3.80 a gallon average.
@9mpg= $253
@14mpg= $162
You just saved $91 in only 600 miles. Now say you drove 6000 miles a year in it. All your driving averaged with the 454tbi you would get about 8mpg. With the 6.0 lets just say it averages 12mpg. Lets also say gas averaged $3.80 all year.
@8mpg= $2850
@12mpg=$1900
Now thats a savings of $950! But economy is just one aspect. On a stock lq9 im guessing you will gain probably about 80hp and 20ft.lb of torque over the 454. Not a whole lot. But if you get better mpg and gain performance. That sure dont hurt! Most important to me would be the driveabilty. How pleasnt the 6.0 would just always be to drive! Ultra smooth, good "feel", reliable. You name it, the 6.0 wins it.