TAF trains will come eventually (even if almost everyone dislikes them)
There is a way, Mauri.
1) Open the Steam directory in your PC (found in, for example, C:\Program Files (x86)\Steam\)
2) open the steamapp directory, then workshop, then content, then 1066780 (TPF2's ID), then 2130149022
*3) open res, then models, then model, vehicle, waggon
4) you can see various .mdl files. they can be opened with any text editor (blocco note)
5) open for example "fs_centoporte_grigio", then scroll down.
6) near the end there should be the lines "availability = { yearFrom = 1975, yearTo = 0, },"
7) change yearfrom value (1975) to whatever year you like
REMEMBER TO SAVE (it happens a lot to me) and close the file.
9) repeat for all the carriages you want
* From "res" this is the mod itself. Every mod has this directory structure. The content of the files (such as .mdl) may vary a lot from mod to mod. Every modder has it's own style.
yearTo is zero because it's impossible to go back in time, therefore service end for the vehicle = infinity
It is advised not to touch the game's files found in TPF2's main directory as it may brick the game entirely.