Pete97
What is easier is going to depend on how handy you are with tools.
I think the simplest fix (for me) would be to get the HF(pull start) engine and have a running tractor.
BUT sometimes it is better to start with everything attached (but not working) I did this with a rotospader and re engined it (with a HF engine)
Maybe you should be patient and keep looking until a better option appears?
Can you buy the non running 10xl and wait until you can find a "parts tractor" with a running engine?
Have you considered mounting an electric start snowblower tecumseh engine to the tractor (110v or 12v?)
There are lots of choices. All have some advantages and disadvantages, but YOU are the only one who can make the "right" one for your situation.
BE AWARE that no solution for this tractor, is as simple as bolting on the engine and go.
Small fry explained above that the "clutch" will need to be modified for any "new" engine to work. It is doable, but is more work which will need to be done. Here is a web page to help with that
http://vsgt.aforumfree.com/t188-ss-and-suburban-engine- swap-fyi
here is video that will help you see how it works with the clutch mounted to the tractor body...
http://www.youtube.com/watch?v=3ANDRB49aiA