My Lemans was getting barely 10 MPG. My 2016 Sierra gets 22 on the highway, 17 in town. The cost of this changeover is about $5,000 - including the offsetting sale of the 440 Pontiac and M22Z transmision.
So if the Lemans averages 20 MPG with the L84 5.3, the difference is 10 MPG.
A liter of fuel in Barcelona is around €1.70 currently, 3.8 liters per gallon make that $6.46. $5,000 will buy 773 gallons, times 20, would be about 15,000 miles to recoup my cost of changeover - about 2 summers of driving over there.
That said, I did have at one time a 462/2801/200-4R/3.55 combination that would pull down 17 on the highway and mid 14's at the track. It would have been much less work to have stuck with that. But I am never happy unless trying something...
besserspat: I first had 3.23's with the BRF 200-4R, much happier with 3.55's as the 3.23's would lug at 60 in OD.
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