I'm thinking about putting a scope on my 1955 model 70 .270 but am concerned about two things:
1. Will value be impacted? Because it is pre-drilled, I'm assuming it wont hurt the value since the scope bases can be easily removed??? Is this correct?
2. Can the iron sights remain on with scope including the front sight hood?

1. Value will not be impacted if done properly. Select the correct mount. They are available from a variety of sources and manufacturers. They are bolt on / bolt off.

2. Depends on the scope set up you select.

My own pre-64 is scoped and was scoped sometime in the 1950's (or at least with 1950's components / scope). When I rebarreled it with a pre-64 barrel I decided to remove the rear sight and because the muzzle had been damaged, deciding to shorten it to a more handy length made practical sense.

Most pre 64's I've seen with a scope mounted with minimum barrel clearance will have the rear sight replaced with a blank in the dovetail slot. The front sight and its hood can normally remain in place without causing any issues with scope optics. (If you need to remove the rear sight or any screws from the scope mounting holes, keep them in a safe place so you can still put it back to original.) As long as you don't drill any extra holes, your value shouldn't suffer too badly. Adding recoil pads, rebarreling, modifying barrel length, length of pull by shortening a stock, grinding a bolt handle, or any other permanent modifications involving removal or drilling of wood or metal or their original finishes will definately hurt resale on a collectable rifle. Some earlier pre 64 rifles were not factory drilled & tapped for the rear mount, they sometimes have an inteference issue with the bolt handle and the scope when the scope mounts selected are too low. At one time, it was common practice to remove metal from the bolt handle to gain clearance for the scope rather than putting higher mounts on. To keep the collectable value in tact it is very important to choose a mount that suits your scope and rifle so you dont need to modify anything on the rifle.

Thank you for the great information. Now I need to search out the proper mount and scope....

Any recommendations on mounts??

For a Model 70 that old, I would suggest either a Weaver mount or a Stith mount, if you can find one. A Weaver K6 ought to be just about perfect for the whole combo.

Great, thanks!!!