Hi all who stocks s/steel rad neck??? can find alu weld in not s/ steel Lenny
my mate does this sort of thing after having trouble sourcing the same things himself.
see this post I put up a while back for his contact details:
stainless stuff
can make the tank on prob, it is jest the bit for rad cap i need to find/buy in s/steel Lenny
if you give him a call he can give you the thread details, then just get a local m/c shop to turn a neck up and get a vauxhall cap from the breakers