[MrPbody]

First things first. Take the trans out and take it to a reputable transmission shop (not a general repair shop, unless they're known for transmissions). Pay the "tear down" fee to get it diagnosed. Chances are, the parking pall is broken, and the internal linkage is not working properly.
There's no such thing as a "patch job" on an automatic (at least one you plan to keep). A "bench" rebuild (you took it out, and will be putting it back in) should cost in the $500 range for the TH350, uness there's significant damage to "hard" parts (drums, shafts, etc.).
You didn't say which engine was in the 'bird, so I can't tell you if you have TH250 or TH350. There's a remote chance of it being TH200 (if 301 Pontiac V8). If it says "METRIC" on the pan, it's a TH200, and you should dispose of that one and get a TH350. Success rate of rebuilding TH200 is low, even for the best transmission guys. TH250 is a "light duty" version of TH350, and has a band adjusting "lug" on the top side, not present on TH350. For 6 cylinder or daily driving, TH250 is adequate. For any performance applications, TH350 is minimum.