Is this frame suitable for singlespeed/fixie conversion?

Hi,
Please bear with me, as I have a lot of questions, all regarding an old 1980s(?) Raleigh steel road bike frame that I want to build up into a fixed gear/single speed bike. Having never owned or ridden a singlespeed bike before, I'd like the flexibility of a flip-flop hub so that I have the option of a fixed sprocket and a singlespeed freewheel, so don't have the option of using a chain tensioner.
Firstly of all, this is a picture of the dropouts of the frame.

After thorough reading of Sheldon Brown's 'Singlespeed Conversions' page I'm quite encouraged. The dropouts are fairly horizontal and whilst the non-drive side has plenty of space of for lateral adjustment of the rear wheel, the drive side dropout is very shallow. Is it likely that this is going to give me enough room for adjustment to achieve a good chain tension? Sheldon Brown doesn't seem shy about modifying frames, so would it be a good idea to file the drive side dropout longer, so that it gives me a similar amount of adjustability as the non-drive side? If so, how would be the best way to go about doing this and would it still be strong/stiff enough to deal with the forces exerted by the drivetrain? I'd have to buy some metalwork tools, so any suggestions?
Secondly, the width between the rear dropouts is approx. 117mm and the fork dropouts approx. 93mm. Is this about normal and do the O.L.D. measurements of modern wheelsets vary a lot? With the old wheelset, the rear stays and the forks had to be prised apart a little bit to fit the wheels in (I hear this isn't a problem with steel frames) but would prefer not to have to do this if I'm buying a new wheelset.
Thirdly, the headset on the frame is pretty awful:

The forks have a threaded steerer (1" I think) with a quill stem. Are there any good headsets available for threaded steerers these days (I've had a look online but am completely confused), or should I consider buying some new forks and go for an Ahead headset?
Sorry for all the questions, but any help at all would be greatly appreciated!
Please bear with me, as I have a lot of questions, all regarding an old 1980s(?) Raleigh steel road bike frame that I want to build up into a fixed gear/single speed bike. Having never owned or ridden a singlespeed bike before, I'd like the flexibility of a flip-flop hub so that I have the option of a fixed sprocket and a singlespeed freewheel, so don't have the option of using a chain tensioner.
Firstly of all, this is a picture of the dropouts of the frame.

After thorough reading of Sheldon Brown's 'Singlespeed Conversions' page I'm quite encouraged. The dropouts are fairly horizontal and whilst the non-drive side has plenty of space of for lateral adjustment of the rear wheel, the drive side dropout is very shallow. Is it likely that this is going to give me enough room for adjustment to achieve a good chain tension? Sheldon Brown doesn't seem shy about modifying frames, so would it be a good idea to file the drive side dropout longer, so that it gives me a similar amount of adjustability as the non-drive side? If so, how would be the best way to go about doing this and would it still be strong/stiff enough to deal with the forces exerted by the drivetrain? I'd have to buy some metalwork tools, so any suggestions?
Secondly, the width between the rear dropouts is approx. 117mm and the fork dropouts approx. 93mm. Is this about normal and do the O.L.D. measurements of modern wheelsets vary a lot? With the old wheelset, the rear stays and the forks had to be prised apart a little bit to fit the wheels in (I hear this isn't a problem with steel frames) but would prefer not to have to do this if I'm buying a new wheelset.
Thirdly, the headset on the frame is pretty awful:

The forks have a threaded steerer (1" I think) with a quill stem. Are there any good headsets available for threaded steerers these days (I've had a look online but am completely confused), or should I consider buying some new forks and go for an Ahead headset?
Sorry for all the questions, but any help at all would be greatly appreciated!
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Gears - Obscuring the goodness of singlespeed
Headsets no problem - Stronglight do them; see http://www.spacycles.co.uk/products.php?plid=m2b2s115p0
I reonvated a mates old 531 Peugeot using the steel version of the A9 for a whopping £8.50. Just give Spa a ring and they'll sort you out.
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Gears - Obscuring the goodness of singlespeed
Singlespeed/flip flop hubs are 120mm across. Just stretch the frame a touch. Except for some modern MTb hubs 100mm is the norm at the front. Bet yours have been squeezed up a bit. Any traditional screw on type hub can be respeced and maybe redished to take a single speed so maybe cash could be saved there. If you want fixed look for some old track wheels or poke around ebay.
2.Plenty of good threaded headsets about. have a look at SJSC website. They have a good selection of stuff for traditional touring bike.
Front width is normally 100mm, rear track is 120mm, somme old 5sp are 117mm (and 3sp also). Rear road is now 130mm, the old standard 6sp is 126mm. Where are your wheels coming from? (I have always tended to building my own but not everyone thinks that way). If getting wheels in and out poses a problem use a piece of threaded bar and two nuts to spread the dropouts 5mm to lmake the job easier, no problems.
I would cut the gear hanger off and file the righthand dropout back to the same depth as the left. Otherwise a half-link chain will help if the dropouts turn out too short.