I think it's not cropped up for a few reasons. They are great simple, cheap, tuneable conversions but got a bit scarce.
120bhp stock, easily tuned to 175bhp, bolt on goodies and a few tweaks will see 230bhp.
I'm unsure if there's been any improvements on that. There was a few engines with improved internals in the pipeline which were expected 250+ but then it starts getting into f7p turbo kind of budgets, and equally low budget, low boost f4r's.
As they became cheaper I think the b18's fizzled out?
Happy to help with info, although a little rusty. I did do a guide before this site popped up.