Hey Dave, Its Dave. I think I can help you with that Olds motor. The 3 means its an Oldsmobile block, the 5 means it was built in 75 or 85. the F means its a 260. If you want to confirm this, a 260 oldsmobile has a 3.5I bore and a 3.8I stroke. Remember, All 307s came with 4bbls stock and 260s came with 2bbls. As for 350s, I do believe they came with both. If your friend needs any help with that motor, Feel free as IM me. Later