Royal Mfg. was a company in colorado that distributed planes from the marutaka company of Japan, they no longer exist as a company.

Royal kits are some of the best scale designs, the kits are much sought after, even though there a bit antiquated in there building style(lots of blocks of wood to carve into shape) and some other older construction methods, hardwood engine mounting rails, stuff like that, but the variety and scope of the range was outstanding.

I am currently doing a scratch build with heavy modifications of a royal FW190A8 kit now http://www.rcuniverse.com/forum/m_5620546/tm.htm

as for your engine you will probably find some info in the "golden age" section or the "glow engine" section as well, might even come across someone who has some instructions for that particular engine as for performance not too sure, I don't even remember them when I first started in RC in "76