Need advice on single axle truck purchase (day cab)

Boxcar kid. I have a Dodge 3500 and it does ok but I'm want something that will last a bit longer. I'm looking at single axles. I haul 15k to 20k local trips. I'm wanting to haul around 30k same local trips. Can advise me on horse power

 

It is not just horse power, there is no substitute for cubic inches. Long stroke inline 6's can produce a lot of torque at moderate RPM for many miles.
Next step up from your Dodge Cummings is the 8.3L in maybe a Ford - Srerling , Freightliner or a IHC 530. There are several others like the C7 and Mercedes but I have limited experience with them. A 530 pulled 28 ft doubles over rolling hills when the big truck broke down. Just saying it was the little engine that did and I don't thank a C7 or the early 8.3 (C series) could. Around 275 HP and up.
Also have to have the correct transmission and gearing for what you are doing.
If I were doing that I would look for a air ride. Cummings 10 or 11 liter, Detroit 11.1, 350 Mack 9 or 10 spd type truck able to run about 70. That's a little larger than you thank you need but save money because they are on easy street all the time. Something like an FL70 with an 8.3 would probably be a good set up for you and the Allison is Ok. However they can be like a garage, a year after you build it it's just not big enough.
I know some of the smaller engines have some outstanding HP figures but most lack the guts to pull large loads dependably on a regular basis. If they do the drive train is not up to it and most importantly is the lack of brakes.
Don't know about the new ones and the emissions scare me but still want to be in the 9-10 liter area. Just my opinion. Good Luck.

 

I have a 2006 Freightliner Columbia single axle day cab. It has the 12.7 with the EGR VGT delete done. 10 speed with a 23k rear with axle lock. Right around 500,000 miles on it. It runs great 500 hp at the wheels. If your interested pm me.

 

Avoid Maxxforce Internationals like the plague - no one I know that owns one has had good service out of them. IF you must buy an international - avoid the 8600 cab - go with the longer hood series (the 8600's have either the Cummins ISM or MAX in it - the longer hood has the ISX and more room to work on them.).