Transmission/Tv troubles

[GMCSTEPS]

Hi guys, I'm new to the forum and the world of these amazing trucks altogether. I recently acquired a 65 step side gmc with a later model 305 and a 700r4 auto tranny and so far I have been going through and cleaning up quite a few of the POs mess.

When I originally test drive the truck it was revving to what I thought at the time was excessive rpm before shifting to 2nd, but the guy assures me that since it is a 3 speed that level of rpm is normal, and not knowing any better I believed him. Now that it's back at my house I discover that it is in fact a 4 speed and rpm range close to 4500/5000 is absolutely not normal to shift gears. I never got it to shift into 3rd during the test drive bc we were just in a neighborhood, but now I've taken it out and tried to push it into third and have just gotten higher rpm but no shift from 2nd to 3rd.
I messed with the tv cable a bit and now all I have is 1st and reverse. It has a factory style tv cable with the "d" shaped button for adjustment but when pressed and moving the throttle there is no clicking into place like the guidelines say it is supposed to. Ive checked the governor gear and it looks brand new and the tv is connected to the cable at the transmission. So bottom line is, does it sound like it could be something out of adjustment that I can tweak and if so what, or is the tranny fried and I am in for a new one. Sorry for the long post but I know you guys can help, thanks in advance