Here's my backyard way to get there.
I believe your Doug Nash will have a GM 32 spline out put correct?
Park a male Greek Coupler on the end of it, about $90 worth.
Use the earlier Vette 7.5-10 bolt diff that will give you lots of tall ratio options in a 2 series from 3.08 up to 2.136 (aka 2.14)
Use a Torsen or Eaton 2 series carrier that does not have spider gears or cross shaft.
Mike at B&J can make you a female Greek Coupler for the 10 bolt pinion, about $120.
Mount the whole mess in your chassis, no need to adapt them together.
Without spending piles of money I think the tallest ratio you can get for a QC is 4.11, now you have to overdrive the crap out of it either with the spur gears or the trans to get the final drive ratio you're looking for & that is going to cost you HP.
The 4L80-E trans is something you might consider too. It's plenty strong enough in stock form for everything you will shove through it, has a .75 overdrive, 32 spline output, a lock-up converter & is easy to make full manual with no ECM. We hung a used $150 Craigslist cheapy on a twin turbo Duramax in a street rod five years ago that's done Drag Week & has over 20k hard miles on it since. I call that value! A 2WD Turbo 400 short tail housing will bolt up to a 4WD 4L80-E trans to make it a short 2WD.
Sid.