I have picked up a Trek 600 frame and fork and am building up a bike from parts I have lying around. I am modernizing the bike and putting on 8-Speed STI shifters and the associated cogs, wheels, derailleurs, etc. I have a Shimano 2300 square taper crank that I am going to use but I am having trouble figuring out what length spindle I need to go with.

The bottom bracket is a 68mm English thread so I have that nailed. I believe the original spindle was either a 113mm or a 117mm in length. I have a feeling since the crank is a Double I should go with the 113mm spindle.

Any comments are appreciated. Thanks.