While some of the conversion outfits out there are making the T56 swap work in the Rover chassis, I think they either customizing the frame or making custom adapter parts to make it work. There are other options. I'm swapping a LS into my 2-door RRC, so most of my research will work for you. I assume you want to retain a manual transmission, as I did.
The RW-Eng swap was originally built around using the automatic 6L80 from the 5th Gen Camaro. That's got some drawbacks, as it's difficult to control except with an OEM ECM. Reliable third party control of the transmission is iffy, at best.
For years the most promising solution was to use an adapter from Marks4WD to the Rover bellhousing and a built up R380 which mates natively to the LT230. The issues are it requires a unique starter (custom machined starter housing) and smaller flywheel. These parts are available from Marks, but they aren't that appealing. And you have to beef up the R380.
Another alternative is to use an AX15 transmission. Use an adapter bellhousing to mate the LS to the AX15. Then use the RW-ENG AX15 to LT230 adapter to mate the transmission to the transfer case. While the transmission isn't a T56 with it's double overdrives, the AX15 is close enough to the original T56 that torque capability is close. It's not close to the T56 Magnum, which is really a TR6060 built for aftermarket use.
RW Eng adapter:
https://rw-eng.com/products/adapter?_pos=1&_sid=f281918ea&_ss=r&variant=12031997378602
Bellhousing:
https://quickdrawbrand.com/product/ls-to-ax15-bellhousing-adapter-kit/
Bellhousing:
https://www.advanceadapters.com/pro...o-jeep-wrangler-ax15-adapter-bellhousing-kit/
Adapter plate that uses a stock GM 621 style bellhousing:
https://www.novak-adapt.com/catalog/adapters/engine-to-transmission/ax15/kit-gmax15/
Quickdraw make some other bellhousings for stronger transmissions, but I don't think there will be room in the chassis or tunnel for them without a lot of extra custom work.