Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hero : your faucet hole adaptation looks close enough to the original to make me think that’s what they started with 
The 1977 version is shown on left side of the following pic , the latter 1980s? JEMCO version is on the right. That little “spout tip” is a way I can roughly spot early from latter engines. The early engines also appear to have “silver colored” connecting rods versus latter “brass colored” con-rods.
From your book and engine pic my amateur opinion is that your #8000 Thermal is looking like ~1978 Griffin type. 
{Note,PM Research still sells some parts for these engines, I may try a ‘dry fuel’ burner. https://www.pmmodelengines.com/product-category/solar/solar-accessories/ ]