my 1956 dodge postal van

You maybe able measure wheelbase & swap the chassis for like GM g-body or s10 or dodge durango & make the drivetrain more Autozone friendly & rat rod look outside !
Its different ?

the wheel base is a short 95" . i am wanting to keeep everything as is other then a motor and tranny swap , but like you say , it would make it easier to find parts by swapping the chassis .