65 Barracuda no Reverse

Daughters car lost reverse dropped tranny pan and filter was really bad looks like its been quite some time since its been replaced . The servo seems to be in one piece but new to Mopar cars , can anyone advise on what to look for to diagnose this ? I do have access to lift . The car seems to be wants fight between gears when put in reverse and move when put in neutral . 273 with Torque Flight Thanks Bud27