Last weekend I put a Quick Performance 9" in my 69 Chevelle. The perches and mounting points were perfect, though I did use double adjustable uppers and adjustable lower control arms. I am going to post pictures of the whole process next week probably. Also, I had to make spacers for the perches because there was so much slop with the springs. No way around that. Turned out great though.
The ears on the 9" are about 1" or so higher than on the 12 bolt, just because the housing is bigger. Mine has 4 mounting points for the lower control arms so that you can adjust them. The Quick Performance housing is VERY NICE. My uncle, who is a welder and machinist, was very impressed, and he has VERY high standards when it comes to workmanship.
Rather than having them welded on, I'd look at buying a housing that's already done. Don't worry, it will still be a ton of work. We spent 21 hours on mine this weekend, and we still have a few hours left (bleeding the brakes, adjusting the e-brake, setting pinion angle, etc.). That's just the way it is with this stuff.
I hope this helps some.