I'll let you know what I have done but not completed yet. The 51 is in the rod shop getting a whole new drive train, brakes, and more.
On the radio front I hand made from 1/4'' birchwood a shelf that fits above the window rim (which helps hold the wood frame in situ). It is held on the sides by the wood frame and above the headliner and in the middle I brazed two threaded 10x32 screws tapped the smaller hole in the roof then brazed the threaded cab roof to hold them in place. These fasten to two L brackets on the wood frame where the pockets are w/ locknuts. This shelf has two pockets on either side to contour the cab's roof for tapes, glasses, CD's, maps etc... In the center I have cut out a rectangle the size of the newer radios on the market, approx. 2 - 2 1/4'' high by I think 7'' long. It is centered; just below that I built into the wood frame two aux curtiosy/ map lights from a mid 70's volvo . Each one of those has their own swtich and are about 1 1/4'' x 2'' facing down. The Harmon Kardon speakers are from a SUV Rover and have a nice mounting where a ring unscrews and these can fit thru a simple 3'' hole and get tightened. I thought I'd place these in the door kick 'removable' panel. I have removed the in cab gas tank and may place two speakers there or simply buy the stereo speakers that can fit where the old speaker was. I had to remove the headliner anyway so I have also added shoulder belts along w/ 'Dynamat" sound deadening material to help kill the road noise and tinny sound from the sheet metal panels, ie roof, doors, back panels. I also added two sided jute material for quiet, insulation and noise in all those areas. The new headliner should be able to fit the back section and the front will get cut short and fit just above the radio (whatever type radio we buy). I also cut out two sections of the seat kick panel just below the driver/ passenger legs so full access can be gained to store / grab whatever is placed there w/out removing the bottom seat cushion. This has been padded and carpeted. Another curtiosy light is fitted to the center 8'' wide section of the seats kick panel center section so when Caroline opens the door the floor and two underneth of the dash, lamps will light up using a door jam switch.
The old stock mirror still fits where it should but I will probably ebay buy an auto dimming mirror e/ compass and temp. The visors will probably be ford explorer because the visor once down, have a second flap that helps w/ the sun in your eyes.