Not 110% but given the buzzing it sounds plausible
Not easy if they are not working but.......
The easiest way to tell if you have dim dip is to have engine running, put side lights on. If you have NO illumination in headlights, you don't have dim dip. If you have a dull glow from the headlight you HAVE dim dip.
Pulling the pink thing (removing the relay) does stop the dim dip but it also kills the dip. IIRC (the resistor is buried in the front wing wiring loom )
Found this - Use a fused link to test.
Disclaimer - check with wiring diagram first I'm at work so cant really double check
Not sure about the bell housing itself,
The backplate, however If I remember rightly the housing is completely different as the 300 has a recess for the crank seal where the 200 just has a hole for the seal to be pressed into
Bit messy but it was as it was going in...........
Cheepo Chi-wan-eze manifold, air pressure switch and overpressure valve from Ebay, cheapo reulator again from Ebay, Air tank from Scrapper skip lorry
Expensive'ish bit was the coelescating filter to take any residual oil out of the air (not good in your tyres) as I use a Air-Con compressor oil drip fed £40 which was stil very cheap of yes...........Ebay
There are some pics IIRC on my build thread (linky at bottom sig), def measure 20 times and cut once
All the measurement are in the fitting instructions
Quite a pig to fit and it took longer than I thought it would, but I fitted the internal bulkhead removal bar as well