Having a 15 month old I've been dealing with the car seat issue myself recently and have done quite a bit of research into this especially because I'm 6'3" so front seat space is obviously an important factor! Initially not even figuring that space was a factor I looked solely into safety and we went with this model from Britax:
https://www.amazon.com/Britax-B-Agi...ents=p_89:Britax+USA,p_n_age_range:2364747011
Super safe, great reviews and test results, you can buy multiple bases so the same car seat can be taken from one vehicle to another etc. etc. At the end of the day though once installed I was squished up on the steering wheel, so the car seat always was positioned behind the passenger seat. My son loved this seat up until he got about 1 year old then for some reason he just hated being in it plus he figured out how to unclip the harness where is clips together across his chest. All in all it was a great seat for a newborn but once your baby starts getting in the 10+ month range and has picked up some weight hauling a 20lb baby strapped into a +/- 35 lb car seat in an out is not going to be an easy feat for your wife (and possibly you) especially if your Jeep is lifted.
At 14 months my son exceeded the maximum height of the above car seat so I had to replace it and started looking for other models that I could use rear facing (which I want to keep him in as long as possible for safety) and after a lot of research I ended up picking up one of these in June for my wife’s car:
https://www.amazon.com/gp/product/B005MQRAAK/ref=oh_aui_detailpage_o07_s00?ie=UTF8
Again super safe, has a solid steel frame construction, exceeded all crash safety tests etc. Having a steel frame the thing literally weighs a ton so you are not going to be taking it out of one car putting it in another. So if you have multiple vehicles, plan on getting multiple seats. As it is a convertible seat though, it will literally stay with you as your child grows and not have to be replaced after 15 months or so when they exceed 31" in height. So it can be used as rear facing, front facing and as a booster and the seat has a 10 year life. So it's a buy it once and it will last your little ones entire childhood type seat. Super comfortable, has memory foam padding and my little guy loves being in it! Installed rear facing I use their optional Angle Adjuster which cost about $9 and it frees up even more room to recline the front seat. I can fit with the seat installed behind the driver seat but usually keep him behind the passenger seat so that I can see him. Another beauty of this seat is that they are very narrow compared to other seats, so it is possible to install 3 of them across the back seat, or you can do 2x next to each other and still get a passenger in the rear too!
Knowing what I know now I would have skipped the Britax car seat/stroller combo that he out grew at 15 months and just bought the Diono seat and a separate stroller. It would have save money in the long term! I actually liked the Radian RXT so much that a few weeks ago I just picked up a different model from Diono for use in my truck and Jeep which is this one:
https://www.amazon.com/gp/product/B00ISS2S8I/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
It's almost the same as the Radian RXT but just minus the adjustable height head support wings which can be a little uncomfortable for taller children and is more critical for infants lacking neck strength (so I'd go with the Radian for a new born). As an added plus it matches my jeep lol and the little guy loves the bright color, cup holder and memory foam padding! Hope the above info helps a little in your search!
On a side note I posted some Amazon links and I apologize if it violates any rules but I'm doing it simply to point to specific models as there are so many different seats available from each brand and I wanted to be specific.