vintage nishiki frame -- BB/chainline question
 

I am getting an 80's Nishiki Riviera GT frame that I'm planning on using for loaded touring. From reading in the forums the BB housing is most likely 68mm, and the rear spacing is 124mm (planning to cold set to 130mm). I'm planning on using Shimano 105 hubs with an 8sp cassette and a Sugino XD triple crank (26/36/48).

The frame comes with a BB installed and I'm wondering if I'll need to replace it. Is it likely or unlikely that an 80's BB will work with the hub/crank setup I mentioned above?

Also, if I decide to replace the BB I need to know what spindle length to use. How do I determine this?

The bottom bracket spindle length is usually determined by the crank, not the frame. Your crank should come with the recommendation for the correct bb length.

Why 8-speed? Unless you already have 8-speed shifters, I'd go with 9-speed. There is a much wider availability of cassettes for 9-speed since all current MTBs use it and road 9-speed stuff is still widely available. Your 8-speed 105 hubs will accept 9-speed cassettes (and 10-speed for that matter).

I'm going to use friction bar ends and I already have an 8spd cassette.