You don't have to feed hearts for its taurine content. Taurine is found most abundant in all muscle meats--the more active its muscle, the more taurine it contains. This is why hearts are usually included to feed cats, but you can also supplement with more rabbit meat, such as the leg, for example. Just note that rabbit A's natural taurine content will probably differ from rabbit B's. I think this is why Dr. Pierson recommends buying the powdered taurine supplement. In addition, grinding bone & meats and refreezing can slightly degrade their nutrient content. It's good to have on had, just in case, too. That way, there's no mistake Leelu is getting an adequate amount. Btw, because taurine is water soluble and is flushed out via kidneys, there's no real harm of overdosing. Have you tried your local markets/butcher? It may be another source of rabbit meat for you. Not sure if BC area carries Smallbatch, but they also make ground rabbit mix in 2 lb chubs (dog section). There weren't veggies/fruits/grains in it.
If you ever come down to WA state (in the Seattle area), there are pet stores that also carry our local brand, Natural Pet Pantry. It contains meat protein with supplements already added in, no veggies/fruits/grains, and also includes rabbit. My two cats love their rabbit, but it's one of the most expensive meats (along with venison)
Hope you find a good supplier; rabbit meats are just harder to come by. It seems that farmers who supply them have their ups and downs in rabbit populations throughout the year, believe it or not, lol.
10cats--as MM stated, the amount of raw you feed your cat will depend on your kitty's weight. My two are almost or about 10 lbs, I feed them about 2.5~2.75 oz/meal/day, sometimes as high as 3 oz. I guess it's close to their wet food portions. The only thing with feeding raw is, most people find it easier to transition them after feeding them canned. Can't say your cats won't eat raw straight from kibble, but it definitely helps if they already eat canned. Maybe you could try offering a small piece of raw chicken to see their reaction? Initially, I had to top my raw off with some freeze dried meats to get them to try and eat it. Some cats may also be picky about their texture, too (canned & raw). Good luck!