Hard shift/wont shift past reverse

[ChevLandCruiser]

Last week I bought a non running '66 Land cruiser with a chevy drive train for $500, out of what I guess would be an early 80s, but I don't know, and when I went to buy a new starter to put in it (which is all It needed after we fixed the timing the guy had messed up), the bolt pattern for the starter was that of a late 70s buick 350, none of the chevy ones matched up, but this is definitely not a buick 350 as the distributor is, as my ford loving father says, "in the wrong spot"(rear of the motor) but that is another thread for another time, after we got it running we went to drive it and it wouldn't shift past reverse, in and out of park and reverse fine, drives in reverse fine, but not past reverse. So we got under there and disconnected the linkage and shifted it right on the side of the tranny (th350) and if we shift it slowly from park to reverse it will stop at reverse, but if we move it one continuous motion, it will slide right past reverse and go into neutral/drive gears fine, we can then hook the linkage back up and shift between neutral and first just fine, but once we go back past reverse it wont shift back to neutral or drive. Im going to pull the pan off here in a few days and check for anything bent or missing, but I don't know a lot about automatics and this is the first th350 I have ever dealt with (kind of hoping its shot so I can have an excuse to throw an sm465 in it and never worry about it again) so I wont really know what Im looking at. Sorry for the long post. Any ideas would be appreciate.

Also, it sat for a little over a year without being moved before i bought it if that might be of any help.

Thanks,
Robert