There are some guidelines on how much oil to add to the different parts based on full capacity rating. You are going to replace the dryer aren't you?
I had a manual laying around here somewhere that had the various capacities of different cars or you can try www.ackits.com.
You will want to add a percentage of total to the various parts that you replace, remove, etc...
If it were me I would flush everything out and start from scratch.