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a lot change to a top fill radiator and junk th eheader tank, screen was bottle in the boot, or tucked inside a pannel somewhere, wiring look extended and run down the chassis legs and tucked away as much as possible or run under the engine and up.
a lot junk the heater and it's plumbing, simplify the coolant pipe layout etc.
then you neet to cut off / grind down and smooth out any unused studs and brackets, grind and fill pannel joins, fill any now unused holes etc
tbe a lot of the properly smoothed ones are little more than show cars, overheat, suffer from airlocks and leaks etc.
can look superb though.
i think on an e30 you could clean up the bay a lot just by rerouting the wiring that runs down the wings and moving the washer bottle somewhere. i started doing it on my metro, moving the battery to the boot, and running the wires on one side out through where the siderepeater wires usually go, and up allong between inner and outer wing, exiting when they were as close as possible to where they needed to go.