Measure your frame's bottom bracket shell again and you should get 68 mm. I'd be VERY surprised if it isn't a standard English threaded 68 mm bottom bracket. If the current bb is a Campy Veloce, from that period it should be a cup-and-cone type and removal will require a lockring spanner, pin spanner and a fixed cup spanner. For a one-time removal, I'd have an LBS do the job as buying the tools isn't worth it for a single use.

Assuming it is an English bottom bracket any of the Shimano Hollowtech II cranks and bottom brackets should fit. 105 or Ultegra are fine and the crank and bb don't have to be from the same group. Suitable external bearing installation tools include Shimano's TL-FC32 or Park's BBT-9 or BBT-19. You will also need the Shimano TL-FC16 to set the non-drive side arm torque and Park's BBT-9 has this tool built in. A torque wrench and a 5 mm Allen key bit is needed to torque the nds clamp bolts properly.