Given the Beechey stuff in the BJ collection, there's a famous car that ran the 58mm crossover Weber set up, which no one's picked up on, and that's the Nova. If the rocker covers are 327 style, that could make sense, too. The RF guard showing is a suitable colour to tie it in.
The only stumble is that engine, from memory, was a Traco & you'd expect their rocker covers to have replaced the pressed tin items.
Ken.