Can anyone offer advice?

Advice on what?

I was referring to advice on replacing vintage 1948 windows with doors. I want to preserve the 1948 character while incorporating modern functionality. The house is waterfront, with an old growth tree canopy in Jacksonville, Florida. I'm wondering what materials might be recommended and if anyone knows of historical renovators in Jacksonville, I would appreciate recommendations. Thanks again.

Also, the house is on a crawl space  and will lead out to a patio.

I suggest you provide the dimensions of the window, the height of the ceiling, a description of the heater below the windows and how you would replace it, and photos of the windows from the outside what lies beyond the windows.

Certainly a worthwhile part of upgrade more useful given the waterfront location that wasn't considered in the original plans. Fleetwood is a quality manufacturer with a dealer in Jacksonville Beach- Fenblik.

What room is this window in. It really is a beautiful window, by the way. Not sure, I could bring myself to replace it with doors.

9' ceilings. There is no heater beneath the window. What you see is a 9 inch deep window sill and baseboard. The window needs new glazing, and sometimes leaks.  The room is part of an old hunting lodge.

The old window in the middle is 14 feet wide. The sside windows are 38 inches each.

I would use an Outswing French door, with sidelights in a combination to give you as close as you could get to the width of the orignal windows. this door is a Marvin Elevate, 10’ wide, 8’ tall. With additional matching Casement or fixed windows at each end to give you the total width you are looking for. The door and fixed panel windows combination in the second photo are 18’ wide. if you didnt like the outswing, i would change that to a 3 or 4 panel slider