It looks like it is all one part; I did remove one from an LT77 box last year and as far as I remember it was two parts. The cross member was round and the box mounts were separate. I will be taking the R380 one out but it will be about 3 weeks before I get that done as I am going away today for two weeks. If you have not got the info you need by then I will be in a better place to help.
As for the mounting holes, They look the same on the chassis.
Regards
Frax