The Retirement Modeller will allow members to model retirement benefits from 55 (or current date if older) up to their 75th birthday. It will default to your current age if you are older than 55. Different schemes have different minimum retirement ages, that would trigger an actuarial reduction if you are looking to retire earlier than the scheme normal pension age.
You can adjust the age that you wish to retire within the retirement modeller, but you cannot model two different retirement ages for the two separate schemes simultaneously. The modeller shows what each part of your pension is potentially worth at the age you select. In the circumstances described, you could model your benefits at age 60 and then at 67 and the modeller would show you what the classic and alpha pensions would be worth at both ages.