TH350 not shifting properly

[GothamCity]

Guys,
My car is a 1972 olds and I had a b & m floor shifter installed. I replaced the old cable and the new cable is longer than the orginal one. I have replaced the intake with a performer rpm,and made sure to connect the hard line which connects from my tranny to soft hose to my intake. The issue is I have trouble shifting my car. I put in reverse and give it gas and it doesn't move, I rev it and it then clicks and moves backwards. The same with going into drive it doesn't consistently shift unless I really rev it. The fluid level looks okay. The transmission kick-down cable was disconected when I bought the car, it has about 80 k miles on it. Any ideas before I take it to the shop of what could be causing this. I have TH350 tranny...