How wide is the original axle? If it's 140+mm, then you can have a 135mm OLN width and still get 2+mm protruding from the ends. If not, I'd get a new axle. I found some 135mm replacement kits at mybiketinley.com for a good price. Someone else said they could find new axles in San Jose, CA for $2 or something. But if the axle is too short, get a 146mm.

I have a collection of 2mm, 3mm, and 5mm aluminum axle spacers for 10mm axles. If, as you suspect, someone bolted on an 8spd freehub body and didn't re-space, then adding 2mm to the drive side might be necessary for chain clearance. If that's too much, I'd pull the single washer on the drive side and put in a 2mm and that would add 1mm which might be enough. This may take a few iterations.

If you're shy of 130mm at 129mm, I'd then go and add a 2mm + 3mm spacer on the non-drive side axle and bolt things down. This should get you to 135.xxx mm OLN width.

As for axle protrusion, if you're able to use a shorter 141mm axle, I'd split the difference and have equal protrusions on either side of the hub locknuts, maybe 0.5mm more on the drive side just because I'm a tiny bit irrationally paranoid about pulling the drive side out (especially if it's going back in vintage steel frame w/ horizontal dropouts).

You may need or want to mess with BB spindle to perfect the chainline, but usually the setup will just work as is. Now you should have minimum asymmetric dish rear hub ready for 135mm service.