DIY flip is cheap, nearly free, but involves a bit of fab work. A few hundred for the kit if you purchase one. Any donor will be well used, abused, and you should rebuild it. IIRC the rebuild kit for Dwayne's was around $300. Plus cost of the used t-case, $150 and twin stick at 200. Say $1200 or so installed. If you don't re-gear it, which I would. So closer to $1700-1800 with new gears.
If you are looking at a crawl box in front of the 300 ad about $500 for the kit. Bringing your total near $2000....which is damn close to the Atlas 2 speed.
Atlas 2 speed is $2200, brand new, bullet proof and comes in your choice of reduction.
Atlas 4 speed is $2800, all the gear you'd want, etc....
For double the money you get 10x the t-case.
My choice will be the Alas 4 speed for my next rig.