Just got off the phone with Equipsource (Lifan Power USA), and Home Depot.
I spoke with the vendor of the engine per Home Depot's advice. According to Dan at LPUSA, there are no more 99.7cc side valve engines available, and has been superseded with the 79.5cc OHV engine. This engine has the same bore with a shorter stroke than the 99.7cc version to accommodate the overhead valves. According to him, this is a better, more reliable, engine than the side valve engine. He also says that this engine puts out the same power as the side valve engine did/does. I asked about the Aug 2011 mfg. date, and he said that they are also better than the newer 2012 engines as there were more EPA changes to them so he bought 500 of the 2011 engines. He didn't try to pressure me into keeping this engine, and understood if I wanted to return it to Home Depot.
I then spoke to Home Depot to report my findings. I explained to them that, according to their website, I thought I was buying a 97.7cc side valve engine for the price stated, and that I wound up with a smaller engine at that price. I also mentioned that an engine of that size can be had for $80 with coupon. They initially offered me 10% off if I wanted to return the engine to a Home Depot store, and re-order. I explained again about being able to buy an equivalent engine for $80, and they then offered me a $39.99 e-gift card that I could use to reduce my cost of this engine. I need to go to a Home Depot store and have them credit my card with the value of the e-gift card. In essence I will be getting the Lifan engine for $79.01, the same as the HF 79cc engine. I think I can live with that deal, and I'll keep this engine for my Cranbrook build.
I was about ready to throw in the towel, and just return it and buy an HS 49cc kit, but realized I would be paying an awful lot for the accessories. I will want to upgrade what comes in the kit anyway, so I think it makes sense to buy the components I want instead.