Yes, most Ric 5 strings were 4 string conversions. IIRC, the current 4004/5 has a wider than standard neck, but they're not only bloody expensive, but also rare as rocking horse doings.
Retrovibe made a few 5 string Fakers that had a good reputation, but again, because they're Fakers, rare as rocking horse doings again, but at least they are reasonably priced.
If you're after the Ric look, but with a low B, find a Faker 4 string & put the low strings from a 5 string on it.