Been their an done it.
No it will not bolt to a C120 flange, with all 4 bolts, only 2-bolts. have that same type odu unite here, an pop off that scalar an re-drilled it to accept a 120 flange lnb when I was setting up my 1.2m dish here. an it work well but a channel master feed really work a little better, so that is what I am using now. but I am a big beleiver in scalar rings on dishes, they will help any dish perform better when you use the right scalar with the right dish. so I would recomend using it, but play with some other ku-scalars at the same time, but remember to use the same lnb when playing with different scalars, because 1 lnb may be a little hoter than a other. an this is where a CtoN or a StoN meter is really helpfull.
now you may find that the lnb on the ODU, is made by "JapanRadio", an on mine here it was a .7db 100khz, which is a very good lnb. now on some of those style lnb on the ODU will have a small metal plate right inside it wave guide, if you'res has it just pop it out (only snaps in), that was meant to notch their freq that they where using on the receive end.