Yes, it's all the same. The HR strap that was bundled with my 705 is the same one I use with my 310XT. I'm on my second (never bundled) footpod and my third cadence sensor (the original one was bundled, Garmin warrantied the other two, and what they sent me was the same package you might get if you were buying it for a non-bundled set). I've also paired the cadence sensor with the 310 and used it a few times.
The cadence sensor comes with both its magnets. The wheel sensor pickup arm adjusts separately from the body of the sensor, so with a little fiddling you should be able to get it close enough to read both magnets, regardless of your frame geometry. You can place the body either above or below the chainstay, whichever gets it positioned right to read both.
Speed comes from what you put behind you. - Judi Ketteler