E30 rally build — roll cage, suspension, and turbo M50 swap

Great project. I did a turbo M50B25 in my E36 and the Link G4X is excellent — very flexible, good knock control, and the software is intuitive once you learn it. For an E30 swap you will need custom engine mounts — there are a few companies making bolt-in kits, check Garagistic or Condor Speed Shop.

For the wiring, I would recommend a standalone harness rather than trying to adapt the M50 harness. The Link G4X has enough inputs and outputs to run everything including boost control, wideband, and even launch control.

On low boost with a Holset HX35 or Precision 5858 you will easily make 300hp on pump fuel. The M50 bottom end is very strong.

For roll cage fabricators in Poland, check out Racetech Poland or Custom Cages — both do FIA-spec cages and have experience with E30 shells. In Lithuania, there is a shop in Vilnius called Baltic Motorsport that does cage work, but I am not sure if they do FIA certification.

The Drexler LSD is a solid choice. Make sure you get the right ratio for rally — you might want something shorter than the stock 3.73 diff ratio for better acceleration out of corners.