THANK YOU again jerry!
don't feel bad becouse...jeepers I'm old too!
it looks like a lot of people hit you up on that comment.

Excellent advise ya'll!
Tom M. 
     your second post told me exactly what I needed to know.  My understanding is that once I have replaced the trucks (which will be necessary because the flat car leans to one side and this becomes quite evedent when I put the pup trailers on it.)  the different types of shanks, "upper", "center", and "bottom" mount are chose to off set any difference in height that I may need to fix.  that is the part that I couldn't figure out when I was pouring over all of the choices out there.
THANK YOU ALL! THANK YOU ALL!
     I will be back with other questions

gl-
I don't even know what those parts are...yet, but thank you for planting that seed of curiosity because I will find out!

jward
thank you for the easy alternative but the truth is I am so excited about doing this now that I am going to go "whole hog". 
  I have toted this old flat car around from home to home for decades just waiting for this time.  the kids are grown, I am out of the army and I won't be living out of boxes and duffel bags any more...to me it is a monument not an old toy!

jerrys ho
     I don't see the "thread but thank you for responding.

YA'LL ARE GREAT!

I am getting a lot of great information in a short amount of time. this is great.  My main concern is choosing the right bachmann ez mate couplers.  I haven't even tried to figure out the trucks yet.  how can I figure out which version of the easy mate coupler to buy rather than buying a pair of each to see which one matches height  and or any thing else that will effect the performance.  should I take care of the trucks first, or both the trucks and couplers together?
     the Tyco flat car was made around late 70's to mid 80's time frame, it is plastic and it seems to be slightly weighted.  The load for it is two "pup" or "piggy back" type trailers.
    Thank all of you for sharing your knowledge with this old ammeter!

I have an old old Tycho flat car that is the only piece left
of my
> first train set. I would like to replace the trucks and couplers
so
> that it will work well with my new bachmann dcc train. as I pour
over
> all the new choices you offer I am simply overwhelmed with top
shank
> med, length etc. what do I need to update this old car?