This means building a wall that spans the entire distance of the opening and is strong enough not to move until you are done.
Making garage door opening taller.
If you have the room on the back side of your garage you can make your garage into what is called a jack jill garage.
Because garage doors are usually sized to snugly fit the dimensions of the garage itself making the door larger usually means making the garage larger.
One way to do it would be to get wall extensions for the entire the garage and then cut the roof of the garage off lifting it up to the height you want it.
That is the side where your truck is to go you can build out on the back side.
Before removing the header you will have to support the roof above it.
I removed some siding and and re did the trim on the top of the door and then recovered every thing with aluminum and installed new rubber garage door sill around the opening.
If you are lucky it s in good shape and either made from 2x12 s or even better a glulam beam.
The height of the rough opening must be 1 5 inches taller than the garage door you intend to buy.
Easy to do and it can solve alot of problems.