According to the 1955 brochure. 740's were drilled and tapped for scope mounts at that time. I would assume that they were ever since. Another interesting note: the .280 caliber was only listed as being available in the January 1958 catalog yet the production numbers I have show that there were a boat-load of them made in 1957:
A-lo grade - 8,832
ADL - 3,160
BDL - 32
1958 - 59 the numbers drop significantly:
A - All purpose - 127
ADL - All purpose - 9
Hope that helps. The .280 is a great caliber; I have a 7600 in it. Good luck!