My advice would be, for what its worth, get a goodish camera (good bellows, reasonably stable/tight standards) and invest in glass. If you had favorite 5x4 lenses, then get the equivants for 10x8, eg if you had a 150 and 240 get a 300 and a 480, or there abouts. Don't forget process or barrel lenses (no shutter) use the old hat trick and a ND filter.

When I went to 10x8 I bought a Burke & James for $300 US, have since moved to a Kodak MasterView which I got for about $800 US (sold the B&J for about $280 so can't complain.) Still have my 5x4 gear plus I use reducing backs (5x7, 5x4,) if you want a bizarre look (have done this only once, whole series of circumstances) try 10x8 with a 5x4 reducing back and a 120 roll back!

Other option is monorails (cheap, not so portable)

Anyway, my 2 cents worth...