I'm trying to remember this episode and I can't. They all start to blur together after a while.Ed Asner To Reprise Role From Original ‘Hawaii Five-0′ In The Series’ CBS Reboot
I guess the scenes from the original will be used as flashbacks. All mention of the character's names that are used in the reboot will not be used in the flashbacks of course. Though mcGarrett could be because it could be Steve's father.Ed Asner is upgrading his status on Hawaii Five-0 from a guest star to recurring. In a very unusual series guest arc spanning 36 years, the multiple Emmy winner will guest star on CBS’ Hawaii Five-0 reboot in the spring, reprising the role of August March, which he played in an episode of the original series in 1975.
In a first for the new Hawaii Five-0, footage from the original series will be featured in Asner’s episode. It will be from the actor’s first Hawaii Five-0 appearance in an 1975 episode titled Wooden Model Of A Rat, in which August March (Asner) was an up-and-coming world class smuggler. Now a reformed man after serving 30 years in prison for murder, March lives on O’ahu and is approached by the Five-0 to assist on a smuggling case.

That's really cool that they'll be able to get a high-profile guest star to come back like that. I can't wait to see how they rework the footage into the new episode.