If you use two 8 ohm speaker cabs, you don't need to daisy chain them. You can just plug one into each output jack.
The Sunn 2000S came wired two ways;
Either with a 16 ohm "Speaker" jack and an 8 ohm "Ext Speaker" jack or with an 8 ohm "Speaker" jack and a 4 ohm "Ext Speaker" jack.
It seems you have the 8 and 4 ohm wiring, but you might want to check it as all Sunns from that era have 4, 8 , and 16 ohm taps on the output transformers and it's simple and not uncommon for somebody to have switched them in the last 40 years.
Let's assume you have a properly wired 8 and 4 ohm amp.
If you use either jack by themselves they are as marked, when you use both jacks at the same time they default in parallel to the 4 ohm tap.
So, you can use two 8 ohm speaker loads using both jacks simultaneously, or one 4 ohm speaker load to the 4 ohm jack, or one 8 ohm load to the 8 ohm jack.
Now, a small rant.
Everyone here tries to be as helpful as they can, we all share a common interest and we keep it civil and friendly.
BUT: All of this information has been covered ad nauseum on this forum. Both loudthud and now myself have answered your question specifically, and over the years that same question has been answered over and over and over and over and over; I think I've probably answered it personally a dozen or more times.
It gets very tedious.
USE THE SEARCH FUNCTION!
Opinion questions are different, but these simple tech topics get asked repeatedly and the only proper answers aren't an "opinion" or open to discussion; there are the way it is, period.
And... most of them have been covered over and over and over etc., and it often seems like new posters don't want to put in any effort beyond throwing it out there and expecting someone else to do their legwork for them.
It gets frustrating.
So... Sorry for the rant; it's nothing personal, welcome to the forum and I hope you enjoy your 2000S!
Just please do a quick search before asking basic questions, just like on any enthusiast forum.