I'd say exactly what 17Ram2500 said.
Before counting slogo as a troll, consider that there are ALOT of people that don't have the experience, parenting, training or a place to start learning about finances.
Consider this an opportunity to help the fella out with constructive advice. Given the overall nature of his post, he seems like a genuine person without alot of education.
Also consider $600 after taxes is GOOD money in some parts of the country, provided that's a running average and not a best of 2019 paycheck.
Although, unless the big truck is needed to earn that paycheck or absolutely needed for recreational purposes that one can afford to do, then it is not a good idea. Buying it for a status symbol to roll down main in a 1 horse town might get you some p_ssy and it might also get you 2 more dependents on your tax return by next year!
I can apply a $40k a year salary to a geographical area that is depressed that I'm intimately familiar with and I can tell you the average income is not that high, and while you could support a, say, $600 payment, it's not the right choice IMO. $600 payment (if you're lucky), another $100-300/mo insurance full coverage driving record dependent. Say 1 tank a week = $300-400 in fuel. Now you've used up 2 checks.
Property tax, utilities, upkeep, etc on the "free" house. Another paycheck or close to it. Cell phone and food, nother $100 a week. Yeah it's doable, but I wouldn't be comfortable with it. My greatest car payment to net income ratio was about half of a week take home = truck payment(me and the wife's income and 1 vehicle, I had a company truck). We could have extended ourselves further and many do. 25 years later, now, we could go buy as many new trucks, today, cash, as we could fit in the garage AND shop and not have it be a huge financial burden. I know many people in the same class, same business, same incomes, same age, same kids, same same same and they currently have far less retirement saved up, less equity, less toys and generally far less financial stability.
These same people had 2 new cars, brand new with brnad new payments, bigger house, etc. Didn't take too many years and it was "hey, we sold our boat, damn payments were killing us, can we go out on your boat" type conversations to start happening.
We are somewhere between hard working, fortunate and smart, IMO. Slogo, sounds like you have a jump on life in the fortunate department and appears you are on the right track in the hard-working department. Just make sure you're smart with your money. Doesn't mean you can't have any luxuries and have to eat beans, but you already got a RZR with a payment. Don't drown in payments.
The point of this is not to brag, but to stress to slogo that this seems like an extravagant, unnecessary expense based on what info we have presented.
There is also a certain sense of pride and comfort knowing you are not only financially secure, but emotionally secure enough to not "have" to have the newest rig on the block. I might buy a new $60k Mega cab to replace that 07 tomorrow or I might drive it 10 more years. It looks and sounds good and it's nice knowing I could get a new one if I wanted to.
To answer the actual truck question, if you must have a newer Cummins, I'd go '14-15. Better bang for the buck than a nearly new one and not the first year of the new emissions.
07 5.9 Mega, G56, SB Single disk Ceramic clutch, OE 1 piece Al driveshaft, 60hp Industrial injectors, Triple dog, Glacier 2mic filter, BD exhaust brake, ATI Super Damper, BD steering brace, Firestone bags, Big Wig swaybar, 4th Gen 20s and some home made Stableloads.