Speed graphic. You can mount anything on one of those. A 4x5 one is my preference but you might like the miniature one with a 120 roll film holder as it would be more convenient (though I prefer 4x5 sheet film processing; spooling up rolls of film for development is a pain in the ass compared to dealing with sheets of film in the dark, but of course sheet film is more expensive - probably 2 or 3 times the cost per shot compared to 120 roll film).
Ask the seller about the focal plane shutter (to make sure its working properly). Ask about the bellows. Make sure the back is functional and the ground glass is included.