If you have already built a few AK's, then you could build yourself a '74. It's not too different, just a little more 'picky' on the tolerances.
If you haven't build a few AK's, then you should just buy one.
Nowdays the prices for '74 kits are a little high and the prices for already built '74's are a little low, so the $ gap is pretty narrow. At nearly $400 for the kit and $100 for the receiver, $ for rivets, tools, finish etc. You get within spitting distance of $600 and that's not worth building it IMO if you can get one already built for $600.
When it comes down to it, you'll be probably a little better buying from ORF than building one. If you get one already built, you don't have to worry about if it will function or not, and what to do about the finish, etc.
I would have no problem buying an ORF '74.
Of course, some people enjoy building regardless of the time involved or pennies saved. I, on the other hand, enjoy shootin more than anything.