Replying to Adapter Advice

Okay, so when I initially bought my gh3 I was planning on just investing in mft lenses, but, now after seeing the limited amount of good mft glass, I have decided to buy an adapter so that I can use my old Nikon glass.

What adapters do you recommend? Is it worth buying one with an aperture built-in like the speed booster? Also, I have a nikon 70-300 which is quite heavy so Im looking for something that can support a decent amount of weight.

Thanks,

Ben