The IRS is far superior to the swing axle. I would keep looking.
The torsion tube front end is not hard to install. In fact, many owners have replaced their stock torsion tubes with the adjustable front end, so that they can remove some of the bars to soften the ride and then readjust the ride height.
Pinkmg (in real life known as Mark) posted an excellent description of the entire process. Search for “front suspension”, you should be able to zero in on Mark’s post.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)