Sounds like interesting bikes. My short time with a Norton educated me on how much effort these old gals need to start.
The strength you have lost will come back- trust me on that one. Maybe not 100%, but it definitely gets better. I think I am as strong as I was before, but for some reason- I don't have the stamina I used to have, and I have a hard time knowing when to slow down. You know how kids run, run, run, then hit a wall? I don't know where the wall is. So- i guess the point is that you'll get a lot of it back. Take it slow but steady.