Need advice, please (ex's poor choices)

I'm so sorry you have to deal with this. I can't imagine the stress you're feeling. Kudos to you for trying to find a way to keep your children safe.

There are a few reasons that kids are safer in the back. One of course is air bags, but if there are no air bags in the front seat, that point is moot. Another reason is that the back seat is father from the point of impact in a frontal collision.

In situations where there is no other choice, there are a few tips that will help. One is putting the seat as far back as possible... we usually recommend this when there is a front air bag, to keep them away from it since air bags can be dangerous for young/small children. In this case, it would keep them away from the dash/windshield in a crash. Also, if they fit in a harnessed seat, that would be optimal (as opposed to a booster or just a seat belt). This will help hold her upper body back in a crash. A seat belt will as well, but there is more opportunity to be out of position prior to the crash (leaning forward, sideways, etc.) whereas a harness holds her torso upright all the time. EDITED TO ADD: I see now that you have two girls, one in a harness, and one in a booster (sorry, missed your sig stats the first time I read the post, oops!) If the driver's seat has an air bag, I'd put the harnessed child in the center and the booster child outboard. Another point to consider is that boosters can only be used with lap-shoulder belts (never a lap-only belt!) so if the center seat has a lap-only belt, your boostered child HAS to be outboard (assuming the outboard seat has a lap-shoulder belt).

I'm sure others with more truck experience will be along soon. Good luck to you, I hope you can talk some sense into him.

In your place, I'd pick another battle.

While it would be safER for the girls to ride in a vehicle with a rear seat, a properly restrained child can be safely transported in a pickup. Let him win the battle for what vehicle he drives, in return, ask for his commitment to best practice car seat use at all times.

I agree. What he's doing is legal. If I was divorced, I don't think I'd want my ex having any sort of say in what I drove.

Trucks are not unsafe for both of girls to ride in. Put the harnessed seat in the middle and the booster on the side with the shoulder belt.

You might point out that if he wants to do something with his gf that they wont all fit in his truck and defiantly not if she has her children along. Maybe pitch the back seat to him that way. also if it is a standard it is going to be hard for him to shift with anybody in any form in the middle.

I agree, trucks are not unsafe and a properly restrained seat will be fine in a regular cab truck. When I had my daughter, that is all my DH and I had was trucks (90 and 91 model Chevrolets with no airbags), we had no other choice due to we couldn't afford to go out and purchase another vehicle with a backseat. The carseat was properly installed rearfacing and it stayed that way for almost 2 years before we found the Surburban that I drive now.

If he is in a financial bind, there is a possibility the vehicle "you" want him to get won't fit the needs of his lifestyle (like pulling a camper, etc...), and purchasing 2 vehicles will totally be out of the question. He's not putting your children in danger by having them ride in a truck as long as they are properly harnessed in proper seats, etc.....

We've let DSS1 ride in a truck, just made sure the air bag was turned off. The truck was large enough and the seat was pushed far enough back that he wouldn't have hit anything.