As far as I can tell, all of the ones stamped RD2 on the back will give you 45mm on the 103 JIS BB. This includes the ones with just the sugino crown logo screened on, and I think the ones that just say Sugino in thin type as well (not sure about all of those). The ones with RD-5000 and the ones with the hidden 5th bolt should be fine. Soma still has RD5000's according to their web site.

3mm off is a bit much for most of us to stomach. The easiest way to go is a 107 JIS bottom bracket (shimano, IRD, whatever), and then put the chainring on the inside. 45mm + 2mm wider -5mm for putting it on the inside = all good. A 1mm spacer on the bottom bracket might be in order if you run 1/8" specific chainrings, as the move to the inside is going to be more like 6mm. Minutia, but just sayin'. A 110 bottom bracket won't work for this, as they're asymmetrical -- they're a 107 with a 3mm longer drive side IIRC.

3mm is too much to spacer the cog, you probably won't have enough thread engagement on the lock ring. 2mm and deal with it might be an option, but it would still make me a little nervous.

Sheldon's method for measuring chainline is a little bit jingus, as you have to eyeball the center of the frame tube. I've never been able to do that and claim I was within a mm of the right reading, in theory a 28.6mm circle and a straightedge should give a nice tangent point to look at, but in practice I find it's squint and guess. I prefer to do it by calipering the tube, the tube-chainring gap, and the thickness of the chainring, and then working it out from there, dividing by 2 where appropriate. On the back I just measure inward from the dropout and subtract from half of the spacing.

Everyone forgets that your chainline is very much a function of how good your frame alignment is, and most people's probably isn't as good as they'd think. This is especially true for newer, tig welded bikes -- I've heard 1 or 2 people say their IRO GB bikes were a little bit out of alignment, and even nice bikes can show up at (and leave) the shop a little bit out of alignment. Why this happens and how to measure and cold-set frames into good alignment has been more than amply covered elsewhere, but the moral of the story here is that you should check chainline manually if at all possible. Your rig could be fine on paper, but if the rear dropouts are not centered on the BB then it will be off. Park used to make a tool for measuring chainline, some shops still have them around -- they work, but not well. Another method is to just hold a straightedge against the chainring and see how it lines up with the cog, but you need like a 20" straightedge that deviates less than a mm, which ain't exactly a job for the ruler in your trapper keeper. I have a nice carpenter's square that I pretty much trust for this, YMMV. Do it with the cranks at different angles to make sure slight tweakage in your chainring doesn't figure into the measure. The point here is not so much to be psychopathic about chainline but rather to identify alignment issues.

Also, I say this over and over, but riding even an OK bike without having the BB shell faced is like buying a leather chair and leaving the plastic on it. You have too have a planar surface for the BB to rest against, or nothing is ever going to be straight, and you can align your frame perfectly and measure your chainline with lazers and it will still be messed up. You'll also wear out bottom brackets on a regular basis.

Finally, I've ribbed Sheldon about this before, but if you've aligned a few frames (or a few hundred, as he probably has), the fact that the numbers on his cog/hub chainline chart go to .01mm is a laugh riot. Getting and keeping a frame that precisely aligned would be a Sisyphean task at best. Those numbers (rounded off) are a good starting place, though, and it's worth looking at them when you find a little bit of unspecified funkness in your setup. Again, though, there's no substitute for reality, so measuring how things are on your bike is always the key.