As far as possible parents for the .35 Greevy Express, I used the AmmoGuide "Cartridge Identification & Search" tool to search for cases with similar rim and base dimensions and longer or equal to the Greevy in case length.

Greevy Rim=.600", Searched for between .590" and .610"
Greevy Base=.501", Searched for between .490" and .510"
Greevy Case Len=2.1", Searched for greater than 2.0"

Here's what it found...


There's your .45-70! (This is just the kind of thing that tool was designed for! )

Mike