I think Mk1 escorts have had their day, they will still rise in value but it will be our generation in 10 years time that will be shelling big money for childhood dream cars.
Cossies are a good bet, but also the JDM classics will be big. You can already see R32 GTR's rising in value, clean unmolested versions are rising in value.. followed by the 33 and 34....but I suspect in 10 years the 32 will be the one to have.
NSX's are a great investment but quite expensive now..original Supras are hard to find and rising steadily.
Also if you can find a decent 993 911 for under 20k(hard now) the last of the air cooled Porches are in demand now, in 10 years the will be huge money.
On the Subaru side clean type -r and P1's will also be in demand, both are rising now..fresh import Type r's are staring at 7k now in the UK , 2 years ago the where starting at 5k.. a lot of this has to do with YEN against the pound but also demand...
If I had to choose but, and I wanted guaranteed return.
993 carrera 2
NSX
R32 GTR