I saw this write-up. http://rcrc4x4.com/ProductReviews/SM420adapter/Review.html
That is exactly what I wanted to do for my Cruiser.
Does Marlin have an email adress ? I didn't see it on his site.
I wanted to know what this setup would cost ?

If you can get through try by phone. My guess is it is well covered in the archives of the toy4x4 section where it is probably a little more common? I am sure it is a simple adapter so not too mysterious...

Using what tcase?

the Toytoa SM/minitcase adapter is half of a toy box.

www.marlincrawler.com

I have dual mini tcases behind my sm420 wwwottindustries.com made my adapter..

front half of a toybox is what you are wanting..
wow.. Jason M. didn't know about the ott one..
uses female input 10 spline gear to minicase. then you can run back half of minicase or cruisercase or whatever..

I want to run it just like Brandon has in his write-up with the one Toy mini case on the SM420.
I already knew about the OTT adapter.
I was also thinking of going for the Novak D300 adapter but I think the dual case/low gear options of the Toy mini-case is a way better solution.

I am doing that exact thing in my cruiser now. I opted not to go dual cases because I think the drive line angle will be too great. So I just have the 4.70 gears. You need the front toybox adapter and the 420 spud gear for the Mini case.