Procedure to remove oil from sump in dry sump

Unfortunately, I think the original design plan was to use the oil tank oil temp sender as the drain plug on the early 308 dry sumps. It wasn't a great plan -- you can see in this SPC figure that on the later (circa 1978) 308 dry sump they added a separate drain plug to the oil tank:

https://www.ferrariparts.co.uk/Diagram/Ferrari/308-GTB-GTS-Carburetor/015-Lubrication-System-(308-Gtb)

 

Hi
I avoid using the oil temp sender as a drain for the sump tank due to risk of damaging sender or possible cross threading of the sender bung. Don't believe it was designed to be a drain plug. I don't think it's up to the task of repeated removals. I use a vacuum extractor to remove as much oil from the sump tank as possible, then gravity drain as much as I can from the motor sump, with the car up on jack stands of course. I'm sure I'm not getting every bit of old oil out of the engine, but it's probably sufficient. And, as I change the oil annually, probably no harm done. The trick is not to overfill the system when replenishing the oil. I usually put in about 8 quarts, then sneak up on the level a bit after that. If overfilled, the oil breather system will spit oil into the air box. I've heard stories of overfilled dry sump cars' air boxes draining oil out of the carb air intake plenum onto the ground.

 

The 288 GTO was the same. The pipe threaded oil temp sender is the drain plug. The mistake people make is out of fear over tightening the sender slightly enlarging the threads each time.
Put on your list of things to do removing the oil tank and having a proper drain plug bung welded in the bottom.