Welcome to the forums! Being modular, the house is built in a factory and the stresses are calculated pretty well before they are built. If all they have is a pair of 2x4's for a header and there is space above it to move them up to accommodate the 80 door, you can do it, as long as you extend the jack studs that are holding up the 2x4's so they rest solidly from ceiling to floor, continuously. What thickness wall do you have? Will you have to adjust there as well?

Ok How does that work? All I have are the doors with the pin no tracks or brackets.

Well, the pins are no big deal. You can buy a complete hardware kit at most Box stores or Hardware stores. They come in all the standard sizes for bifold doors. Includes track, brackets, pins/rollers, screws, etc. You may have to re-drill the holes. Some of the pins/rollers may be bigger and will split the door if you try to force them in.