^ BSA or italian Bottom bracket would be a good place to start (Ciocc would probably have Italian thread).
Easiest way to find out might be to contact DeVer direct and see if they recognise it.
There'll probably be someone there who can point you in the right direction.
re: shifters, I'm not entirely conversant with the 600 DT shifter, but I'd imagine you probably need to lose the rounded bits
And bolt the flat bits straight onto the bosses. I had old Campag DT shifters bolted onto square bosses in much the same way as this
^ BSA or italian Bottom bracket would be a good place to start (Ciocc would probably have Italian thread).
Easiest way to find out might be to contact DeVer direct and see if they recognise it.
There'll probably be someone there who can point you in the right direction.
re: shifters, I'm not entirely conversant with the 600 DT shifter, but I'd imagine you probably need to lose the rounded bits
And bolt the flat bits straight onto the bosses. I had old Campag DT shifters bolted onto square bosses in much the same way as this