Type IV motor may not fit. You need to measure carefully. By the same token, there are adapter kits for Subaru flat fours, but again, they may not fit under your MG bodywork.
But these cars weigh about 1900 pounds, give or take a few. You most likely do not need to go to something like Jake’s massive Type IV. He does build GREAT engines though! I know several speedster guys running Jake Raby engines.
I’ve been running a 1641 for years. Am currently upgrading to a 1776 Type 1.
So, to answer your question with a question, what are you looking to achieve with an engine upgrade?
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)