Nice looking truck
Chevy S10 is the easiest. I'm pretty sure the wheelbase is correct as well. My buddy is big into the 47-52 Chevy/GMC and that's what he uses when he builds one. Looks like you found a nice solid shell to start with. That'll make the project move along much nicer.
I have a similar "sickness", lol. Have 2 trucks waiting after the Dart is done to be built. One for the wife and one is mine (now...was hers until she spotted the older one and wanted it more..lol). They are a 51 international and a 49 international. Different than what most go for which is what we like about them.
I was talking to my buddy and he confirmed the s10 extended cab frame is the correct length for the late 40 early 50 Chevy/GM trucks.