You will need to make two nighbouring artboards out of this one.
Then export them each with bleed.
You really made a catalogue in Illustrator? Seriously, this is a job for InDesign.
First things first... it was a huge mistake to create 64+ page brochure in Illustrator. It should have been done in InDesign. Whoever did it in Illustrator, as reader spreads, has no business accepting payment to design brochures.
With that said... Is this going to be perfect bound? If that's the case, the printer doesn't need inner bleed. You'd have to wreck the book's spine to stand a chance of seeing a white edge. And even if they did, ironically, the fact you're sending reader spreads actually gives them image they need for it.
is this full editable in illustrator?
I would save it as pdf first
then createa new page the dimension of printed size with 3mm bleed
place the pdf on the new page
makie a duplicate of it (ctrl c and ctrl f)
stretch/resize the top page manually to touch the bleed (the inner side)
and send the stretched page at the back.
This time you can get away with it cause it's a gradient shading but if it was actual content you would risk either cropping of the graphics or stretching the page with 3mm, which might be noticable or not (mostly not)
hope it helps