It all depends on the load and framing above (sill, bearing walls, etc.).
The 28x52 seems a little narrow for the rough opening for a legal egress window. The height of the window is not a real factor in the lintel sizing. First determine which window is certified as having an acceptable opening (not glass area) width and make sure the clear opening is in compliance with the local requirements (usually42" or 44" above the finished floor).