Find your camper first, then choose the truck to match the weight.
You have to figure out what type of camping you'll be doing. What amenities do you HAVE to have and what can you live without. Ask yourself these questions seriously. It's a hard expensive lesson to find out that your choice was wrong.
We were tenters before getting our TC. I knew I wanted a front bathroom for convenience in the middle of the night. I wanted lots of storage and as much counter space as possible and I had to have a pantry. We wanted a 4 season camper. DH was just thrilled that I had adjusted to the thought of a TC...he could tow the boat easier.
That's a whole other factor. Will you be bringing toys?
All of your must haves and concessions should equitable between partners. So many times guys will say they don't need a bathroom or even running water, when in fact it's a major factor for the wife.
Read EVERYTHING you can on Truck Camper University. It has so much good information. Look up past posts of folks that have asked the most basic of questions. I'm sure I drove everyone here nuts, but they were great. We ended up with the right TC/truck combo (for us) and couldn't be happier.
Take your time and don't hurry the process. It's exciting but use your head not your heart. TCs as it turns out are more complex than other RVs. (In my opinion).