After viewing various commercially available wind deflector options for my MGB, I decided to make one up of my own.
The following is a description of how I made it. You will need some basic welding and fabrication skills to make one for yourself.
Construction of the Wind Deflector
First, I removed the converible top cover support rail (aka tonneau bar). Using 3/4" square tubing, I bent a length to fit to cross contour of the support rail and cut this piece to the length of the support rails.
By cutting and welding 2 forward pieces onto the new cross rail to match the width of the support rail, I then had a matching "U" shape to the support rail.
Using the same 3/4" tubing, I welded spacer blocks to the forward pieces and in turn welded these onto the support rail. I now had a double support rail with a space between the 2 for the tonneau cover to fit between the 2 rails.
After raising the top and installing the rail, I made up a template for a piece of 1/4" thick plexiglass to fit onto the upper rail but also fit within the top when the top is in the up position.
The plexiglass was then cut from the template and attached to the top rail.
The deflector now just fits into the slots for the cover support. To raise the top, remove the deflector, raise the top, and before lowering the rear section of the top, reinstall the deflector. At this time the rear of the top can be lowered down over the deflector.