Traveling with an infant

Since you are in Nebraska, I'm assuming your friend is too.

Nebraska has certified child passenger safety technicians who can help with selection and installation of car seats.

Here is a locator form.

And more information from the Office of Highway Safety.

There are also numerous forums similar to this one around child car seats. Beware, these are like any other forum, the quality of advice and content varies.

car-seat.org

Don't make or rig a seatbelt, that'll be disastrous in an accident.
He needs to use an infant car seat and buckle it into a passenger seat. It can't be behind an airbag (so no front seat ever for a baby) and it must face the back of the car for at least 1-2 years.

Most infant carriers are designed to be strapped in using existing seatbelts... pretty much any seat that has seat belts should be able to hold it securely.

Is there a third seat in the Freightliner that has seatbelts? That should be fine. If the "toter home" has seat belts for a dinette or something similar, those should work.

Fire departments and Police departments are used to "normal" cars when showing how to install infant seats - they may look at your rig with a blank expression, lol! They could very well help you, but you may want to contact the seat maker or Freightliner.

If he took the carrier and Freightliner to the local firehouse, I believe they can tell him exactly where the placement of the carrier should be.

I don't know what his vehicle looks like, no clue what a toter home is :)

He's asking WHERE to install the carrier..

OP- don't know what that vehicle is, but wherever it's mounted it should be installed backwards facing into the seat. Any of the new carriers are built to be strapped in with conventional seat belts and come with shoulder belt securing clamps as well. Tell him to go to a place like Baby's R Us and talk to one of the moms that work there. This forum is about the last place to get good info on babies.

In a high quality baby carrier/car seat
Install seat belts/straps to hold securely in place on floor between the captains chairs in cab