Probably a 115 to 118mm spindle would work. Hard to predict, as the Silstar crank pre-dates modern cartridge bearing bottom brackets by many years. Some cartridge units, e.g., Phil and Mavic, allow side-to-side adjustment to fine-tube the chainline, but they tend to be expensive. If you're having a shop do the work, you could let them figure it out. If you're doing the work yourself, ask if you can return/exchange the cartridge if it doesn't work for you.