727 for pulling and low end torque

Viking the torqueflite is the easiest trans. to rebuild IMHO bar none. Sounds like a basic rebuild will work for you. A great shift improver kit that addresses some of the shortcomings of the TF is made be Trans-go. It's the only brand of shift improver kit I will install anymore as some I've put in actually caused overlap and the trans-go dosen't. Sounds like the TF-1 would work for you. Or the TF-2 if you want a little firmer shifts. I'd also suggest getting a service manual that will tell you the specs on things so you can make sure and set all the clearances so it will work the best and last the longest. A factory serv. manual will work but there's a book out by Carl Munoe called Torqueflite A-727 Transmission Handbook and it's absolutely awesome and better than a FSM. Munroe's the man when it comes to writing books about TF's. I got mine from Amazon books for about $15 if I remember right. It goes into detail of how the trans works and shows mods and the installation of the trans-go shift improver kit. Also gives all the clearance specs and shows exactly how to check them.