Sweet deal man!
I got a '77 KZ650 for $350. I'm in the same situation you are.... building a bobber. HI5!
I bought a sportster tank, and some 10" apes (apes are illegal here), and a brown leather solo seat.
New coils, points, and condensers, one HELL of a carb cleaning, and she also fired right up. I'm about $1200 into my project and only have tires left to buy.
I'm writing exams right now (Petro Eng Stnd), so I haven't put the goodies on yet. I"m still tinkering try to straighten this damned back wheel after the hardtail conversion.
Be VERY careful when you take the forks out - the bottom ball-bearings will scatter all over the floor LOL.
If your wondering, the up-bend on the bottom rails is about 26 degrees from horizontal and it seems to look nice. Need any help/advice, let me know. This is my first build, but I've learned a shit load (and I've rode bikes since I was 5).
Craig