If I ever get a turkey fryer, I am going to do this, which I saw on Good Eats.
Take the frozen turkey and place it in the pot. Fill the pot with water, so the turkey is covered, and then a little more, that will be the level of the oil when cooking. Remove turkey and either punch or otherwise mark the pot. That will be the cold fill level of the oil.
As for a good fryer, my current setup would be cobbled together, using a Brinkmann burner and a tamale pot or my stainless steel brew kettle.
Whip It Off, Chambers!
"perhaps...but then again...maybe not..."