How do I fix my transmission problem on a 1969 Ford Falcon?

I have a 1969 Ford Falcon Futura with 302 Engine and t4 Transmission. The problem is that it struggles to go into gear from a stop. It just feels like its on Neutral. When I rev up the engine then it grabs the first gear about 10 seconds later. It does'nt seem to do this anymore after driving a while.