You can enter your 40 year Straight Line depreciation. If you placed the property in service before 1981, TurboTax will prompt you to enter the Depreciation Method. See the screenshot below.
Accelerated Cost Recovery System–(ACRS) for property placed in service after 1980 but before 1987.
Straight line or declining balance method over the useful life of property placed in service before 1981.
Generally, you must use the Modified Accelerated Cost Recovery System (MACRS) to depreciate residential rental property placed in service after 1986.
****Swapping from 40 year to 27.5 year requires a change in accounting method. You would need to file IRS Form 3115, Application for Change in Accounting method and get approval by the IRS.****
See IRS Publication 527,
https://www.irs.gov/publications/p527/ch02.html, for additional information.