Suggest what used daycab to buy

I own a company and we have two semi trucks. One blew its head gasket and I am thinking to get another used truck and part out this blown one.

Some background. I am NOT in trucking business, I am in machinery moving and scrap business. I and my driver drive two trucks to and from our job sites or to move customers' machines. As such, we get under 20,000 miles on each truck per year. We are very busy in general so the low miles is a reflection of what we do and not that we do not have enough business.

The one daycab I have, 2000 Freightliner FLD, is a big winner, has NO emission equipment and is a strong runner and puller. Cat C12 engine. The other one, Freightliner Columbia with a Mercedes Benz engine, blew a head gasket.

What I want is a truck that is reliable to operate. Fuel economy definitely is not a big deal to me as we drive little (see above). What I want is to avoid electrical problems, other problems, etc. I understand that an old truck is an old truck and I am ready to swap air bags, tires, u-joints etc. What I was NOT expecting is to face complete engine overhaul at 340,000 miles.

My budget is, say, $20,000 at most. I would think under 400k miles. I buy trucks at auctions (Proxibid, Bidspotter, Ironplanet) and not from dealers. I see a lot of trucks being sold.

So... what is the easiest to operate, low maintenance daycab truck you would suggest? What to stay out of?

thanks. Pic below shows the FLD towing the blown Columbia.

 

Yes, if I could get a copy of my FLD I would do that right now. But it is getting harder to find one without too many miles on them. I will keep looking and FLD is my #1 priority.