A-where you paying $3/gallon lol and B-14mpg in your 60? really? both seem generous... lucky if i was getting 12mpg with sniper...and I hvnt seen gas under 3.10 in foreverDepends on how much you drive. A swap is going to run at least $10k if I do it all myself most likely closer to $15k. $15/$3 pg is 5000 gallons @14mpg I can drive 70,000 miles before I spend that amount in gas. But i have to buy gas for either setup. Im doubtful that the LS3 swap doubles my mileage. Maybe gets me to 20mpg?
So this is why I always say don’t do the math. Just do the swap because you want to. You’ll rarely ever be able to soundly rationalize the investment.