As far as I can tell my '62 convert has a leak where the park cable goes into the housing at the rear of the trans. I'm pretty sure there's an O-ring around that cable end. What's involved in changing that o-ring? Do I need to drain the trans before I remove the park housing?

Nope .. just open that allen plug and let it drain a bit from there. And rust and or corrosion is what probably hurt that o-ring.

There is a o-ring you will have some fluid come out that has accumulated in the tail shaft area. removing the allen headed plug then loosening the locking nut on the side tap in the nut to loosen the locking system, then using a screwdriver you need to push up on locking spring and pull on cable to remove. Install you use screwdriver to hold back on the washer to insert the cable end and have it lock. Last time I had to remove the cable I had to unbolt the entire housing with the 5 attaching bolts.

(As far as I know you cant get the gasket that seals that housing most likely you'll have to RTV it.)

Rick,I have about a dozen gasket's and the correct O ring,let me know what you need.

Bill, I'm pretty sure I have a gasket. Is the O-ring anything special or is it a hardware store item?

Rick,the outside diameter is .420,I have an O-ring kit with over a hundered O-rings,has about a dozen this size so I would suppose it's a standard item.

My '63 has the same kind of problem, does the shift cable also use a gasket or o ring to keep it from leaking? Also I put in a deep Mopar pan and ever since it will not come out of 1 st gear and sounds like it is slipping. Any ideas?

If you're just going to replace the O ring there's no need to pull the housing, just remove the cable.