Here are dimensions for a brake booster spacer
 

Here's a drawing in PDF, dwg, and dxf of the brake booster spacer for fabrication.
I put a Miata brake booster on my FB but needed a spacer. It came on 84-85 FBs and FDs but are NLA. I made the drawing and received one from SendCutSend out of 1/2" laser cut aluminum.
The 80 x 60 mm bolt pattern is common across different makes and models, but finding just the spacer and confirming the bolt pattern can be tricky so I went this route.

https://cimg4.ibsrv.net/gimg/www.rx7...61afff6a0f.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...42305b635a.jpg

interesting... So why is the spacer needed? What's the problem that it addresses?
Thanks.

It simply allows a later booster to be installed on an FB or FC, or replaces a missing OEM spacer.
The older FB booster's mounting flange stuck out more, the later booster interfered with a rib on the firewall and wouldn't quite seat.
Also I'm using a later booster to allow the use of a bigger master cylinder for my big brake conversion. FB master cylinders have a different bolt pattern with the 2 studs arranged vertically.


https://cimg5.ibsrv.net/gimg/www.rx7...264fbdf60c.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...2df687f230.jpg

I see.... That's awesome. Thanks.

I love sendcutsend ❤️
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