Is it a modified AR lower, or something?  Just bought a 7.62 kit and read that the mags were problematic.  Any ideas?

I think it is an AR lower,  modified to accept AK47 mags.

Yep and here's alink to the website
www.ar47.com/

I found the website but it doesn't do a good job of explaining what it is.  It looked to me like it was a combo of upper/lower.  I wonder if i can just get a lower and slap a 7.62 upper on it.

You can get a regular AR and put a 7.62 barrel/bolt and shoot it with regular mags/ they just dont hold as many rounds. 20 rounders hold 10-11 IIRC. Some have used the franken mags with good sucess. I just bought this lower. It will accecpt regular AK mags, the mag well is milled a little wider than normal for the wider AK mags. The upper is a 7.62 barrel/bolt with a mod to the bolt carrier, and the upper reciever has been miller a little wider for the wider AK mags. Mike said the DPMS Lo Pro is the best upper reciever to mill since the walls are .25" vs the usual 3/32".  DPMS is out of barrels. The only one I know of is Model 1, but its not chromed lined. HTH