I've just setup a brand new EPiServer 7.5 site (the deployment manager) and installed the allow MVC Templates, and I've installed find..
I've added the new web.config section, as well as installing the required NUGet packags..

I want to do a basic test, so I added the following code initally to the existing search page 

            var myITems = SearchClient.Instance.Search<IContent>()
  .For(q)
  .GetResult();

I am not yet doing anything with these results (that's to come..), but I get the following error:

Type specified in JSON 'EPiServer.Templates.Alloy.Models.Blocks.EditorialBlock, EPiServer.Templates.Alloy.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not compatible with 'EPiServer.Core.IContent, EPiServer, Version=7.5.440.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7'. Path 'hits.hits[0]._source.$type', line 1, position 400.

This is my first venture into Find, so am I missing something here?
One thing I did have to do when setting this up as update the Version of StructureMap, as it as referencing a different version  

I have run the schedule job to index the entire site ..