I restored my E30 325i two years ago. The M20 rebuild is straightforward if you stick to OEM gaskets and a quality timing belt kit from Continental or Gates. Budget around 800 EUR for the full gasket set, timing belt, water pump, thermostat, and all hoses.
For the cooling system, replace everything at once — radiator, expansion tank, all hoses, thermostat, and water pump. The M20 cooling system is simple but every rubber component will be brittle at this age.
I would skip the M50 swap unless you want a project within a project. A well-rebuilt M20B25 with a Schrick 284 cam, ported head, and individual throttle bodies makes around 200hp and sounds incredible. Much more in the spirit of the E30.
5000 EUR is tight but doable if you do all the work yourself. Paint correction alone can eat 1500 EUR if you go professional.
For body panels, check Schmiedmann in Denmark — they have a good selection of E30 parts. Also wallothnesch.com in Germany is excellent for classic BMW parts. For Lithuania, I can source some used panels if you need — I have contacts at a few BMW breakers in Kaunas.
Suspension wise, Bilstein B8 with H&R springs is the classic combo for street and light track use. If you want adjustable, look at BC Racing coilovers — decent quality for the price on E30.
One thing to watch on E30 restorations — check the rear shock towers and the front subframe mounting points for rust. These are structural and if they are gone, the shell is not worth saving. Also check under the battery tray on the right side, that area collects water and rots from the inside.
I went through this with my E30 touring. Ended up spending more on rust repair than the engine rebuild. Get the body sorted first before touching the engine.
