Grimspeed Lightweight Battery Mount
 

https://www.grimmspeed.com/lightweig...caAjMMEALw_wcB

I tried searching to see if someone had used the Grimspeed LWBK in the 86 yet but came up empty handed.
It looked straight forward enough dimensions wise to fit and I really like the construction of it so I went ahead and got it.

I sort of feel like this is a DIY post but at the same time it's so incredibly easy it's more like an engine mod bolt on than anything else.

It does fit securely with relative ease.
https://i.imgur.com/u72F4s7.jpg

First I had to figure out how I wanted to mount it, once I did that I moved it until it rested flush which the mounting hole in the base aligned perfectly on top of this mounting bracket. I drilled it out to fit the original hardware and super glued the oblong nut to the bottom just to hold it temporarily so the bolt can be secured.
https://i.imgur.com/n6KdWqj.jpg

Then I addressed my surface rust.
https://i.imgur.com/WpZ5S4r.jpg

Now with one bolt in place I opted to use a self tapper in the bottom most hole in the top angled bracket. You could just as easily weld a nut or tap the firewall I chose this option for convenience. You can also see there is another mounting point in the bottom of the mount that I did not use but could be as it's a straight shot down into the gap between the wiring harness and the lip edge where the battery sits.
https://i.imgur.com/EGCsN2q.jpg

And voila there it is.
https://i.imgur.com/AtTgn0d.jpg