Here is a quote of my own from another thread regarding that same topic:
Both systems are nearly identical in rules aside from a couple of stand alone issues that don't affect the other system in any way. And some of the newest model releases have rules in them that affect the rules of the other system as well as their own. There is absolutely no difficulty in meshing the two at all.
In fact, I recommend you check out that thread itself. It is a small one but informative and should answer your questions regarding mixing the two systems. Dig it here: https://www.heresy-online.net/forums/...ad.php?t=66674