You were not wrong. Bain also played Guard.
He was a multi-position reserve OL for years before he started in 1983 and 1984, mostly due to injuries.
Actually, Bill Bain was kind of a disappointment for much of his career. Mid-second round draft choice in the mid-'1970s out of USC (would have blocked for All American RB Anthony Davis) and been coached by future Rams' HC John Robinson (probably the Trojans' OC at the time).
Didn't start much and bounced around to a few teams as a reserve-OL. Actually, he joined the Rams under Malavasi and was with them when Robinson came-on in 1983. Back then the Rams' O-Line was loaded with Pro Bowlers, and they usually played an entire season.
When Irv Pankey went-down in Training Camp (I believe) I was concerned that the Rams were in big trouble at Left Tackle ... I was way ... Way ... WAY ... Wrong.