I have recently acquired the responsibilities of managing our fleet and need a bit of guidance!

I work for a metal processing company and we deliver the processed parts to our customers on pallets. We have a few different fords in our fleet for our smaller trucks and some International 4300s. Our Fords haul 23' goosenecks that are sometimes loaded to the max. I'd say the average load is 10,000 to 12,000 lbs but we can go up to 19,000 from time to time.

The rigs we have had so far are as follows:
1999 F350 dually 7.3, manually transmission 210,000 miles - still going strong
1999 F350 dually 7.3 automatic, 212,000 miles- out of action- drivers beat it to hell and back
2002 F550 dually 7.3 manual, 160k miles- great hauler
2004 F450 dually 6.0 manual, 105k miles- been in the shop more than on the road- we have taken a bath on this one.

I am looking to purchase 1 to 2 trucks every year from now on as we open up new processing plants around the south. We are looking for solid used trucks that are around $15,000. I am open to going with another make if it's a better choice for what we do. Any advice or personal experience will be greatly appreciated!