Finally something I have experience in!
Sometimes you just got to love some of the unique stuff Tyco did put out.
I've done it all! Replaced the couplers inside the Tyco "talgo" trucks and changed out the wheels. I have also mounted standard coupler boxes and trucks. You need Kadee kits 23 - 29 depending on the length of the coupler you need and whether it is center, underset, or overset shank. I mostly use Kit #23 but #28 might come in handy too! Best part each kit will do 2 cars!
Inside the kit you get everything you need! You have two choices, you can simply install a kadee inside the talgo truck, while this is the "easiest" to do watch those centering springs(I had to do a little cutting on the talgo coupler pocket to get the coupler to center and the spring to fit, there is a little flashing at the mouth of the pocket that "centers "to horn hook coupler. Just follow the instructions carefully as they are little confusing ( at least they were to me), I did not realize the talgo adapters simply twist and lock into place(and they really do a good job too!)
Second, you could do what I reserve for my favorites, I will glue styrene or brass tube into the hole were the trucks go and then tap it 2-56 for a screw, then you can simply screw the truck in! Then glue a coupler pocket to each end and then drill and tap the car for the screw to hold the coupler top on and the coupler in. Sometimes you end up with a little screw showing and sometimes I have had to add some tube to set the screw into...It's tricky but the hardest part is centering the pocket!. It is intimidating but the good news is there are plenty of cars to practice on!! Ill post some pics of what I have done... let me know if you need any more help!
PS: I agree with everything everyone else said too! Check the weights and adjust because those Tyco cars seemed like they were weighted with whatever they had lying around!
Also a little bit of dull coat goes a long way into changing a toy into a model!!
PS: I just love these "coke" cars!