Hi Peter, and a warm welcome to the forum. It's nice to have another Scott Bonnar owner join us, as we all love to learn new things and tinker here.
There are 2 things to consider here Peter, one is originality and the other functionality....You don't mention your SB model or what make of engine you have on your machine, so I'm presuming that it is a Briggs; in that case the older Briggs are a good strong engine and quite repairable with the help of our moderators and members here, and will keep your machine original.
On the other side of the coin, replacement of engine is sometimes the best option, as in my case. Unfortunately the G100 is no longer made, and I have not heard how easy (or not) it is to fit a GX100. Another consideration is that Honda engines are now made in China and some consider not up to the build standard of the Japanese made Honda's...yet!
So Peter, you have some decisions to make...no doubt you will receive further replies to help you.
Once again,
