When doing a customer BOB conversion, I realized you can’t buy the flanges to match to the BOB exhaust manifolds, so decided to get a batch made.
They are made from 10mm 304 stainless, with a 51mm hole to accept 2” stainless for making your own downpipes.
CNC water cut gaskets to suit these flanges are available below!
https://www.krisdupreysgarage.com/products/bob-2-9-cosworth-exhaust-gaskets
£62.50 for the pair, posted within UK!
Kris