Hi BASimmo, and a warm welcome to the forum. It's great to have another Scott Bonnar owner on board.
Just for your info, Scott Bonnar first introduced the Model 45 in
1968 and as grumpy has explained, the Kirby would be the HK25, 2.5 HP engine.
If this is the case, your machine will have the solid engine deck (as opposed to the twin rail of the later model).
As has been explained in the earlier posts, if overhang is not an issue, the Honda should bolt on easily....the inner clutch half may or may not have to be replaced....that will depend on the Honda output shaft diameter.
What we need now is to post some pics to this thread, using our inline uploader (Instructions
HERE ) of your machine from different angles and some of the chain-case after removing the chain-case cover.
This will allow us to have a look at the chains and sprockets and give you an assessment.

Once again BAsimmo,

to OutdoorKing.
