anyone hear of a h-p big block sawtooth 318?

was looking on local craigslist and found this ad...

We're selling Grandpa's 30 ft. Classic 1968 Dodge fiberglass motor home (rounded aero-dynamic body) with approximately 100,000 actual miles. It is mounted on what appears to be a one-ton Dodge chasis with a unique high performance saw tooth 318 big block engine and automatic transmission.
asking price 1000 bucks. just wandering what this engine may be or is it even a real thing. thanks