Its supposed to be stamped on the core plug on the cylinder head. I say supposed to be because mine wasn't.
Depending on what parts you want its quite easy to work out the model of engine from www.dougrussell.com
in the US. Then you can get the part number you require.
For your info I found ordering from the US cheaper than the UK even though Dougrussell have a minimum postage charge of $41. US parts are half the price of UK parts. Delivery was only a few days as well.
Best of Luck Nick R.
Also depending on what parts you want E Bay might be the answer. Try the Uk and US sites.