I agree. I doubt somebody would go through the trouble of exchanging a steering column just to get an adjustable steering column system.
And if the VIN tip TheBoy suggested also applies to the Opel range, I think these two things give me a good solid way to tell the cars apart.
You also have a good point about the corrosion. As better as the FL protection may be, if neglected both PFL and FL would be rusty anyway.
So I have decided what I will go for.
I will strive to find as late a MFL car as I can in 3.0 manual with as low mileage and in as good condition as I can.
I just like the design so much more. It makes no sense to buy an early FL (remember I need a 3.0 manual) to change the looks back to PFL, just so I get pretty much the same features. A 2002-2003 FL would get me meaningful extras such as the ESP. But as far as I can tell, an 2000 FL gets me basically nothing meaningful over the MFL. And I like the PFL cars so much more. Externally and internally.
So I'm going with the MFL.
I think the Opel designers were inspired when they designed the B1 (PFL) as it looks like nothing else. With the B2 FL I think corporate thoughts took over because it looks very much like other Opel products of the time, specially the Astra G.
But the PFL car has a look of it's own and looks great.
BUT! If while searching I come across a late FL 2002-2003 in 2.6 Manual for the right price and in great, great condition, I would go for that. The goal is a MFL. But I will not pass a 2002-2003 FL which has everything right and for a very good price.
I'm willing to sacrifice power and going with the V6 2.6 manual instead of a 3.2 just to get ESP. But it needs to be the right car and the right price.
So this is the plan!