A 305 CID engine was used on the California market for model year 1980. I believe that was the only year for that engine.
389 cid
It could be a 5.0L 305 CID. or a 5.7L 350 CID engine.
CID = cubic inch displacement HO = high output
Depending on the year the RS typically gets a V-8 engine. Either a 305 cid 5.0 or a 350 cid 5.7 are most common.
Either a 250 cid I6, a 350 cid V8 or a 455 cid V8
4 cyl = 196cid 6cyl = 232 cid 6cyl = 258 cid 8cyl = 304 cid 8cyl = 345 cid
Either a 231 cid V6 or a 307 cid V8
Either a 229 cid V6, a 305 cid gas V8 or 350 cid diesel V8.
140 CID Gasoline Industrial (LSG423)$2350 $1000 HOPE IT HELPS.
Multiply your litre rating, in this case 5.4, by 61. This will give you your cid. 5.4 x 61 = 329.4 cid
Need to know the year of the engine. You will need to ask your question again with that info.