Transmission issues

I have a a 727 transmisson in my 68 cuda. I just replaced the headers and decided to put a summit aluminum transmission pan on it while I had it up in the air.
I got everything back together and went l drive it and I could only get low gear.
Once home the transmission would not go into park. I thought it was a fluid problem but it didn't change with more fluid. I did pull out the kickdown adjusting bolt to reseal it. I do have reverse. I have pull the pan off and did notice the gasket for the filter extention had slipped, but it didn't appear to be obstucting the fluid port.
Any ideas from the transmission experts?
Thanks for the help.
Steve