The 996R was 998cc. The first testastretta engine. A crackin engine and was the basis of the 998's when they replaced the 996's. That engine, although with conventional and deep sumps, went in the 998's and is still used in the 999's in one form or another.
The 998R engine is the daddy. It runs 104mm bore and a very short stroke, can't remember the figures but i think it's shorter than a 748, and gives 999cc's. It's also used in 999R. Only those two bikes use it. It's the basis for homoglating the WSB engine.
The large bore and short stroke make for a very lively motor and hold the potential for serious bhp. Although only quoted a few bhp up on the 998s with a bit of fettling there are good gains to be had. With a lot of fettling you could pole top 6 on the WSB grid
My favorite techy bit is the head gasket............. there isn't really one. 9 o-rings seal the oil and water channels and a single, endless alloy ring seals the cylinder. Don't go playing unless you are serious though. Those alloy rings are £132 each. Yep. Pull the heads and you need £260 straight away, before you even think about what work you're going to do on the engine....................