Fitting three car seats across?

We have two daughters ages 2 and 1. Our girls are petite and rear face still. Lately my husband and I have been discussing a third child but before we even try to conceive we wanted to think about how we would fit three car seats in our vehicles. My husband drives a 2005 Pontiac G6 and I drive a 1998 Ford Crown Victoria. Currently we have two Evenflo SureRide DLX car seats in my husband's car. In my car we have two Evenflo Sympthony LX car seats. The infant carriers we currently own from our daughters are a Graco Snugride Classic Connect 30 and an Evenflo Nurture. As an extra carseat we also own a Graco My Ride 65 LX. I've not actually tried to install any combination of those because I can't see it working. Especially not in my husband's car. His back seat is much less spacious than mine but all car seats in my car are installed using lap belts and locking clips since my vehicle doesn't have LATCH. Dose anyone know of any car seats we could use to achieve three across? Or has anyone achieved three across in like make/ model cars?

I didn't use "infant seats" for any of my kids. Just used a ring song or Baby Hawk carrier (like the Ergo). I have a 2002 Mercury Sable. I could fit three across as long as one seat was a Diono Radian. We rear faced to age three for our kids. So kudos to keeping your kids safe. Sometimes the Diono can "float" above a seat, or fit below larger seats.
I bet the Diono would fit under the MyRide sides to give needed space.
http://us.diono.com/convertible-to-booster/radianr100

This is the one we use. The $40 Cosco Scenera also fits newborns to around age 4. This is another skinny car seat that we have used.

Using the seat belt install in older cars is safer than LATCH. LATCH on older cars generally only holds up to your chid at 40 pounds if you have a huge car seat.