Singlespeed & Fixed Gear - Pics-Questions for my first single speed conversion

I was lusting for a Raleigh One Way when they were British Racing Green two years ago. Then I realized it would make better sense to convert my Bronze Green 74' Grand Prix which is in like new condition (except for not being cleaned) after hanging in a basment for most of it's life with the owner's manual rolled up inside the saddle.

The cheap black plastic Simplex derailers are unsightly and don't shift well so this is a good bike to convert. And I have two other derailer bikes in case my legs can't handle a 42 x 16 or whatever.

Questions:
1. Is it silly to think the cottered crank can remain? I would like to just drop the big ring and leave the 42 without buying a new crank and dealing with Raleigh thread and bottom bracket issues. This cottered set has not given me problems but can they handle the standing and force of fixed or SS riding?

2. I've read through Sheldon Brown's conversion articles. I'm guessing if I can use this crankset with smaller chainring bolts it's just an issue of placing a SS cog in the rear with a new chain of course and getting the wheel respaced and redished?

Thanks in advance from a newbie.
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Go to a shop and order a set of $15 shifters. Then leave this bike as it is. It looks to be in great shape and attempting to convert it would probably be very time consuming and expensive.

The trick with shorter stack bolts on the crank only works with more modern cranksets. Modern cranks have a chainring on either side of the spider. The larger one is on the outside and the smaller on the inside. Generally the inside position will get you close to a straight chainline so people simply remove the outside ring and use shorter bolts. Your crank has both rings on the inside. If you remove the larger ring, you will have to put spacers on the bolts so that the smaller ring will remain in the same place.

If you really want to do it, take the rear wheel to a shop and have them remove the 5spd freewheel and install a SS freewheel. Then put the wheel back in the frame and see if it lines up with one of the chainrings. If it does, you can try removing the unused ring and replacing it with spacers. If it doesn't, you'd be better off getting a new bike. (Return the freewheel to the shop and have them put the 5spd back on the wheel. It'll probably cost about $10 in labor each time). That way, instead of having one bike that required a new crank or a respaced wheel, you'll have two bikes that are being used for their intended purpose.

Not sure if most cottered cranks are this way, but from experience my friend got a 1980's galaxy that we converted to fixed and within the first 6 months the bottom bracket started to give and was completely gone within 8 months. And it's being ridden by a very casual rider with both brakes that get used fairly often.

So you could use them, but plan to need to upgrade soon.