I have an old Global Cessna that I bought that the engine and all electronics were removed,

My question is, There used to be I believe a Saito engine(not sure what size) in the plane, I am trying to put an OS .40 engine back in it, the engine mount is too wide for this. Is this to be expected?, before I ran into this I had assumed that the distance between the mounting bolts was a pretty standard distance. The mount appears to have the ability to be adjusted but I did not have the correct size hex nut.
Anyone have any tips?

Thanks