Singlespeed & Fixed Gear - Crankset Help Wanted... Identification & Recommendation

I'm hoping someone here can help identify what crankset I have, and help recommend what I could replace it with (or if I should bother).

First: What I have. The bike is a 1984-ish 23" Norco Monterey that I've had since new. I've converted it to a two-speed, with an SRAM Automatix S2 rear hub running the supplied 18T rear sprocket. The sprocket is running 46mm from the centerline of the 130mm OLD (fwiw, the frame appeared to be about 126mm OLD, but the SRAM comes as 120mm with spacers to make it 130. It's centered with both spacers.
278914

Second: The crankset that's on it. It came with the bike, and has two chainrings. Smaller is either 40T or 42T (forget which right now) and is held on with the hex-headed screws visible in the photos above and below. The larger is probably 50-ish and is riveted to the chainguard. Bottom bracket appears to be 68mm width, and judging from the knurled and grooved rings on the ends i'd guess it's threaded but I haven't taken it apart so I don't know for sure.
278916278917

Third: Now what?

I'd like to have a single chainring up front, and a chainguard. The existing chainguard would be HUGE even if I ground off the rivets for the second chainring and removed it, so I probably want a smaller one anyway. Unfortunately it's integral to the spokes holding the smaller ring. I *could* just take a Dremel and cut off the outer portion of the guard, but that seems a little too ghetto for me. :) Also I don't know if it would leave me with anything I could use with other sprockets so it might be pointless.

Can anyone offer any useful suggestions? I'm not sure if a bike this old can even take a modern crankset and bottom bracket, or I might just buy one. I see lots of recommendations for the SRAM S300 crankset, which comes with a new bottom bracket. It looks like a two-ring set too, and I really only want one... I'd like to be able to try a couple of slightly larger rings before finalizing everything too (42 or 44T front), so having a "common" size for things would be best.

Suggestions?

Wow... Day and a half and nothing? I guess you have to say something stupid to get a quick response around here! :)

I see Nashbar is selling Vuelta Pista crank sets for $59 right now... I'd need a matching BB but that looks pretty attractive. The BCD is 144, is that a common size, or would I be limited to chain rings from Nashbar/VP?

144 BCD is the most common for track cranks. The Vuelta Pista has a reputation for being very low end. As for using the double chainring on a fixed gear, you might look here (http://sheldonbrown.com/chainline.html) to see how this may or may not work.

SRAM S300 is a track crankset which means it only has one chainring.

You didn't get any responses because of a combination of tl;dr + you didn't seem to have done enough research on your own yet.

Tough crowd. If i'd just posted a photo of the crank and said "does anyone know what this is and what I could replace it with" i'd probably get a dozen replies, the first half of which would be "what a n00b, you need to tell us xxx about your system to answer" and the second half would be correcting spelling mistakes in the first half. I try to answer all questions up front, and people won't read it because it's too long? Yeesh.

Thanks for the feedback though. The Vuelta's looked too good to be true. :) I didn't know that 144 BCD is the most common track size. I'll file that away for next time.

FYI - SRAM S300 (http://www.sram.com/sram/road/products/s300-crankset#/path/term-id/8) is a two-ring hub according to the manufacturer. SRAM doesn't show it on their site, but it appears that there's an S300 1.1 (or sometimes called S300 Courier) for sale as well, i've seen both names on various vendors' websites. I'd about decided that an S300 would make sense, until I came across the Vuelta.

FYI - SRAM S300 (http://www.sram.com/sram/road/products/s300-crankset#/path/term-id/8) is a two-ring hub according to the manufacturer. SRAM doesn't show it on their site, but it appears that there's an S300 1.1 (or sometimes called S300 Courier) for sale as well, i've seen both names on various vendors' websites. I'd about decided that an S300 would make sense, until I came across the Vuelta.

For some reason the S300 Courier has never been listed on Sram's website.

I have a Vuelta Pista crankset on my rain bike. It's alright for the money but the chainring is shaped more like an egg than a circle.

You didn't get any responses because of a combination of tl;dr + you didn't seem to have done enough research on your own yet.

Agreed. Plus, very few people on here would probably be knowledgeable enough or even remotely qualified enough to help with this kind of problem, assuming they even have the time or interest.