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.
Making garage door opening taller.
If you are lucky it s in good shape and either made from 2x12 s or even better a glulam beam.
Before removing the header you will have to support the roof above it.
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.
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.
That is the side where your truck is to go you can build out on the back side.
Easy to do and it can solve alot of problems.
This means building a wall that spans the entire distance of the opening and is strong enough not to move until you are done.
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.
Usually 4 or 8 feet.