Doors and Windows - exterior door trim

I would like an opinion on how to finish out a door frame. French doors have been installed in place of old style aluminium sliding glass doors. I have an 8" cove area on the outside. The area is reinforced concrete. It is inset 1/2" below the external brick on both side and the top. I only have 5/8" gap around the door which means I only have a total width to work with of 1.75" which includes molding around the door frame. Any opinions would be helpful.

I have tried to drill in the concrete. This is proving very difficult plus I keep hitting the steel bars. The steel bars waste the concrete drill bit. Each hole seems to take about 10 minutes.

Since cost was an issue, my initial plan was to place a couple of 1x3 on each side and attach 1/4" exterior hardwood plywood. I now have concerns that the plywood may warp over time, plus the time drilling for the "tapcons" is frustrating. Need advice

Thanks
Jeff

Why don't you try 1X4 or 2X4 pressure-treated boards, rip them down to the desired width and router the outer edges with a round-over bit (or other decorative bit of your choice) for looks.
You shouldn't hit the rebar in the concrete if you use Liquid Nails adhesive and concrete nails to attach them to the concrete wall.
If the p-t is still a little wet-green, you can let them "cure" a few months in the sun and open air, and prime and paint or stain them. (Or, do like I did, and just let them weather a natural gray.)
Just a thought.
Always more than one way to do things.
Good Luck!
Mike

I am hitting the rebar within 1/2" of the concrete surface. Some steel portions are round and some are 1/4" thick flats. I can see both in an area that is broken out.

I am using #10x1.75. Would you recommend a shorter screw if used with the adhesive?

Do you mean mount the boards horizontally? This sounds good if I can overcome the drilling issue.

Thanks for the advice

There are short, twisted hardened nails made for driving into concrete and masonry that you can get in various lengths.
In your case, I wouldn't try screws again.
In fact, the Liquid Nails alone may hold the trim in place. That stuff will really get a grip once it sets up.
By ripping down, I meant length-ways, not horizontally.
Good luck!
Mike