Options on cowl plate
What options were labeled -A50- C11 C87 W51 & how do I tell what engine
came in the car, Here is the vin # 834L43614
The Pontiac Historical Service (PHS) can probably help you.
Your tag shows it was a V8 engine, so it is either a 389 CID or a 421CID. No other engine options were available and there were many HP variants based on fuel delivery and other factors. Check some specific Pontiac sites as well as PHS.