Howdy Wayne,
FWIW -
Don't have measurements on Long stuff albeit Cadillac equipment,
but a Hurst/Mr. Gasket V-gate shifter mechanism measures 7" long x 4" high x about 1" thick. That is the shifter mechanism only and does not include any bracket to bolt to transmission.
Good luck on your build old buddy.
Regards,
HB2
Dissident