Rough park or neutral to drive engagement on 904

650 idle rpm shouldn't be a problem. I wonder if someone blocked the accumulator in the trans? Does it shift real firm into 2nd gear like it has a shift improver kit installed? Blocking the accumulator in the trans is a popular 1-2 shift firmness improvement but if you have a stock converter it's not a good idea cause there's not enough cushion. I do it on transmissions that are using a high stall converter cause the converter slips enough to cushion things. If the 1-2 shift seems like a stock trans my other guess would be a problem within the torque converter.