Rams are not tied to specific platform. If new motherboard have 4 sockets and support pc3-10700 memories with that size it should work. Pretty much all modern motherboards (so if you got haswell it is one of those) should support that speed as 1333 (pc3-10700 reported as 667MHz in cpu-z or other) is standard fallback speed to which all rams get when they can't auto boot on higher.
However you should TEST using Memtest. www.memtest.org There's no guarantee the new motherboard will work perfectly even though it's already working especially since these are mixed.
Run a FULL PASS (roughly 30 minutes for 8GB).
*Since it's a new system, I recommend starting THIS way:
1) Install only the 8GB kit (see motherboard manual for proper slots. Might be #2, #4).
2) Click "XMP" in the BIOS and save
3) run MEMTEST
4) Install Windows, drivers etc.
5) update the motherboard BIOS
6) repeat "XMP" and testing
7) Run for a minimum of one week to ensure stability
8) Add the 4GB kit, "XMP", retest
9) If overlocking, don't overclock the memory or do it very little.