I have been to Fatmans shop many times ...
I stand by my statement ...
The wheelbase, tread width and weight issues should not be ignored. Aftermarket stuff is rarely as well engineered as Factory Ford, GM or Mopar stuff.
A 1939 LaSalle weighs at least 4500 to 5000 lbs with a late model engine/transmission. A vehicle this large ... needs something more substantial than a Pinto front end.
Just my nickel ...