I would do the Lseries conversion as well. i am doing it and is soon to be finished for real. this wet weather on a motorbike is stupid!

use the 180B crossmember and Lower Control Arms, 180B Castor rods.

120Y Gearbox crossmember.
180B Radiator
stanza struts or 120Y struts with sunny hubs leone discs and volvo 4 pot calipers.
shortened tailshaft.
and you should be away.

you can find 180B's relativly cheap or even a L18 and bits from the wreckers.
so you know as well for a cheap brake upgrade, you can use 1600 standard brakes they bolt to the 120Y struts and arew bigger than stock and will pull up the lighter 120Y nicely.