Going to try to reply to several of
@CorbLand questions.
I bought a 2013 toyota tacoma in july that I couldn't pass up. It's a DCSB with only 16k miles. I haven't ever sat in a 3rd gen tacoma but I thought the seat and legroom dimensions were similar. I went through the same debate and really didn't want to get a full size truck since I'm just using it for hunting, offroad camping in the summer, and house renovation projects with a utility trailer. I wanted something smaller for the trails, easier to drive and park in the city, and cheaper than a full size truck.
I've fit 5 full size guys in the truck for short 30 min drives and been plenty comfortable with 3 guys on longer drives (6ish hours). I was the shortest of the 3 at 5'10" and nobody was miserable or needing stretch breaks. It's not a cavernous back seat like the new half-tons but I also don't need that.
I have a 16-month daughter who moved from an infant seat to rear-facing car-seat recently (the worst position for back seat room). Previously, I had the infant seat behind my drivers seat before and definitely had to move my seat forward. My knees were touching the dash but I would've been fine for several hours of driving. Definitely wouldn't have been ideal for a cross-country trip though.
With the new rear-facing seat, I put it behind the passenger seat. Anyone under 5'6" is fine in the passenger seat but I definitely wouldn't plan a long road trip with anyone much taller.
I grew up in rural kansas and had a similar experience to you of sitting on bench seats or riding in the bed of the truck. Unfortnately, modern car seats are much bigger than what our parents dealt with. Car crashes are still the leading cause of death for kids under 13, so its something to take seriously.
In the end, You'll spend about 3 years of each kid's life dealing with the back seat legroom problem until they move forward-facing. So I'd say it depends how many kids you want to have and how spread apart. If you start talking 3-across it's more of a pain anyway and you're into minivan/full size SUV or truck status.
We're only planning 2 kids and I was willing to deal with the occasional tight legroom for a few years to have the smaller truck.