Tell me what type of car it is in. Is it an open wheel Formula car, A sports racer, a Vega, ??? Cosworth used to make almost all of the engines used in Formula 1 in the late 60's up through the later 80's. During that time they were the engine of choice for most Indy cars. They have been an engine builder for NASCAR, many smaller single set Formula car series, many rallye cars. They built a special engine for the Chevy Vega (yeah really) and have much to do with Escort/ Focus engines. I am sure there are many projects of theirs that I don't even know about. Around autocrossing one of John Sheally's Morgans runs a Cosworth BDA (older Fromula Atlantic engine).

They are not engines that an average engine builder should rebuild.