New codes would never allow that.
But, I have been on a staircase at least that steep in an older home and it wasn't too bad.
The proper measurement of the incline of a staircase is actually Inches of rise per foot horizontal. If you use the existing floor as the top step, you may not have quite as steep an angle as you think.
Steps less than 6 inches high are too close.. Steps over 8 inches are too high.
Most staircase builders work toward a 7 inch riser if possible.
The width of the treads needs to be 9 to 12 inches. and the width of the staircase needs to be 36 inches.. You may not have room in your house to meet all of the best parameters, but you may be able to fudge a bit and get a staircase crammed int the space you have. DO NOT FORGET HEADROOM as you go up the steps into the upper floor. You need over 6 ft. of headroom over all of the steps, building codes require 6 ft 8 inches.