The article that was in Model engineer will go a long way to showing you how to machine it from castings and bar stock. Volumes 111 &112 are what you need.
If you intend to fabricate the cast parts then there is no actual specific article that deals with the Vulcan but some web searching will find several scratch builds of similar style engines and the same principals can be applied. I have a series running on a compettitors web magazine at the moment or you can find the original build thread that it is taken from on MEM and Jo's beam engine on the same forum here. Both engines will be at Guildford show this weekend if you want to see up close or ask questions.
J