The hollow metal jamb is a better product. I doubt that your door
is 1 5/8" It will be either 1 3/8 or 1 3/4. I suspect that it is
1 3/4. Contact any local supplier of commercial doors (NOT the
lumber yard and especially not any of the box stores) and get a
price on a 2-8 / 6-8 door. Measure the hinge tops from the top of
the jamb's door pocket and measure the center line of the strike
from the top. Note whether the strike plate is a T strike or D
strike and its size. Any commercial supplier will be able to
tell whose jamb it is and would be able to precut and mortise a
wood door or supply a steel door that will fit. You can also buy
a slab and do your own prep - make sure to read up on beveling
both edges of the door and proper mortise work with chisel or
router.

If you really want to remove the hollow metal jamb:

Easiest would be to use a gasoline Quickie type saw with fiber
blade and slice across the jamb about every 2 feet. The anchors
holding the jamb will be 1/4" wire or 16 gauge galvanized T's.
There will usually be 3 per side and one in the head. The jamb
will be full of concrete.

Wiggle, cut, grind, hit with a sledge until you can remove the
pieces.

Removing the jamb as usable or in one piece probably isn't going
to happen.

--
~~~~~~~~~~~~~~~~~~~~
DanG
Keep the whole world singing . . .


wrote in message
m...
A small add-on to garage is concrete block with one door. The
old door is hollow core and falling apart. The frame is steel
with no apparent screws or fasteners showing. The frame has
coats of old paint and a little rust and I can't imagine how one
would remove the steel frame. Rather than replacing just the
door, it is looking like it would be easier, if we can remove the
whole thing and replace with a pre-hung door. Door is 32x80, 1
5/8".