Ryan,
You can also find the backup rear seals at Moss Motors, British Victoria, and Mini Mania. In my opinion if you are not experience enough with installing them your time and money will be in vane. In most cases these engines are tired having blow-by with to much crankcase pressure. It’s like putting a band-aid on a six inch cut, it just doesn’t work. However if you are into originality and want to keep your engine original, then have the engine line hone with the rear eyebrow in place. This enables the proper clearance for the reverse scroll to function properly, but the engine needs low crankcase pressure for everything to work normally. With LBC’s its best to stay with distributors that specialize in this field. Trying to purchase parts from one of the chain box suppliers will send you down the wrong path and make you confused.