Help please!!!

First off, hello to everyone on the board, I have been reading this board alot lately but havent been a member to now. I am looking into purchasing a 2007 Tige 24Ve hopefully this winter but another boat has fallen into my lap. I have the chance to purchase a 1991 Supra with 600hrs on it, the boat is in great condition with fat sacs and a tower. The only dilema is that the engine knocks but still runs so it will obviously need a little work but the price is very low and I know the guy. I plan on using the boat for a couple of months while I am waiting on my new one but only if I can make a profit off of it. My question is what price range, roughly, would I be looking at if it is a rod or if it is a push rod? Also what do 1991 Supras sell for that are in great condition, besides the engine problem the boat is in excellent condition. Any help would be much appreciated.