This was my calculations....with the 454/T400/4.10's combo in my 76CC avg 6.0mpg @ 60-65mph.
The 6.0/4L80/3.73's in my 99 give me 7.5 mpg over the trip to Moab and back towing the same load in Drive @ 70mph
well it sounded good on paper....really what set me off was the fact that the payoff should be within 5 years or less....warmed up 454 ring and bearing rebuild of the short block, along with cam, intake, headwork, valves, springs and headers was looking like 2-2500...OD 4L80E in the truck, another grand, so about $3500 to make it power worthy of towing the 18K. Now that should have been the end of it, but with more power, who knows where the mileage would have ended up from the present 6...so figuring a solid 6...2800mi/yr avg ÷ 6mpg x 3.75/gal = 1750/yr in fuel costs x 5 years = $8750.
Cummins @ 10mpg (from what I read this should be the minimum with the provided 98Dodge's drivetrain) x 4.00/gal...1120/yr x 5 years = $5600, so the difference of $3250 is about the same of what it would cost me to rebuild/update the current drivetrain, and of course I would still be wanting FAST after having installing it on the Maiden...another 3K right there. But without the FAST, the total cost of the 454/4L80e combo and fuel for 5 years is about $12250
The Cummins swap and 47RH trans is $3600 up front (including fuel to get it home) - say 750 for recoup of parts sold/and scrap of the leftovers, so $2850...now I know a bunch of little crap comes up, one of which isn't so little with an in bed fuel tank of 75 gal or so, lets say $750 for that stuff, but in reality it will be $1500 cuz you have to double everything and take twice as long as your best estimate, so now we're at $4350 to get that drivetrain in the truck, + the $5600 in fuel costs will put it at $9950 for 5 years of upgrades and fuel cost. Leaving a difference of $2300 in favor of the Cummins swap.
Any better ways to talk myself into this now?
The 6.0/4L80/3.73's in my 99 give me 7.5 mpg over the trip to Moab and back towing the same load in Drive @ 70mph
well it sounded good on paper....really what set me off was the fact that the payoff should be within 5 years or less....warmed up 454 ring and bearing rebuild of the short block, along with cam, intake, headwork, valves, springs and headers was looking like 2-2500...OD 4L80E in the truck, another grand, so about $3500 to make it power worthy of towing the 18K. Now that should have been the end of it, but with more power, who knows where the mileage would have ended up from the present 6...so figuring a solid 6...2800mi/yr avg ÷ 6mpg x 3.75/gal = 1750/yr in fuel costs x 5 years = $8750.Cummins @ 10mpg (from what I read this should be the minimum with the provided 98Dodge's drivetrain) x 4.00/gal...1120/yr x 5 years = $5600, so the difference of $3250 is about the same of what it would cost me to rebuild/update the current drivetrain, and of course I would still be wanting FAST after having installing it on the Maiden...another 3K right there. But without the FAST, the total cost of the 454/4L80e combo and fuel for 5 years is about $12250
The Cummins swap and 47RH trans is $3600 up front (including fuel to get it home) - say 750 for recoup of parts sold/and scrap of the leftovers, so $2850...now I know a bunch of little crap comes up, one of which isn't so little with an in bed fuel tank of 75 gal or so, lets say $750 for that stuff, but in reality it will be $1500 cuz you have to double everything and take twice as long as your best estimate, so now we're at $4350 to get that drivetrain in the truck, + the $5600 in fuel costs will put it at $9950 for 5 years of upgrades and fuel cost. Leaving a difference of $2300 in favor of the Cummins swap.
Any better ways to talk myself into this now?
I come home for lunch every day.. 
