l have a few old ferrari-lancias and the leather in cracking in our older one, best quick fix?

Sounds to me like the leather has dried out and needs to be moisturized. You probably know more about leather creams then l do so I'd find something good and rub it on.

If it is already cracked you can replace the panels that are bad or give it a lot of leather cream to soften the leather and help it last a little longer.

use a foam cleaner on the leather so it wont cause it to dry up and eventually crack. this will keep the leather moistured and it will last longer

If you indeed owned a D-50 Lancia Ferrari,you would certainly not be asking questions on about anything related to such a museum piece.This car is a priceless automobile and to even suggest that anyone who owns one would ask how to do anything related to a D-50 on this forum is ABSURD.

l have never heard of a Ferrari Lancia, except for the formula 1cars that Lancia gave Ferrari, Which Ferrari made a few improvements on. If you have one of those take it to a leather specialist. ,now if it is a FIAT- Lancia, duct tape is good enough.

Try leather repair to soften the leather