get a 10si
there are a bajillion of them out there, meaning good parts support for years to come.
sure.. you can get newer and smaller and pay lots more.
cs130 is a choice if you need smaller.. but it will cost ya.
a good cheap 10si can be had for 30$ with your core, new.(reman)
that said.. if you 10dn has a tach drive.. you might be able to sell it's core to a 3 cyl owner needing a rebuildable 10dn, for more than the 5-15$ core money..