Adjust door size in block supporting wall

I have an existing door on a block wall that enters into the garage. It is a non-standard size and I would like to make it larger.

It has a ~6" poured concrete lintel. There is a second story above (the area directly above the lintel is unused living space).

If I can remove 6" to the right of the door and the 6" lintel above the door I will have plenty of room to frame in the new door.

What would the process be to replace the poured concrete lintel with a steel lintel? (To avoid having to re-pour a lintel)
Will I have enough room on the left side of the door to support the steel lintel?

Does it make more sense to remove one course of blocks and replace with a pre-poured lintel?

What would you do in this scenario?

Any suggestions would be greatly appreciated.

Thanks!