Hey, no offense meant. I just posted my experience, and I honestly haven't seen an A-body 8.25. Like ever. They only came in the 73+ cars, and the vast majority of those had /6's and 7.25's. Even the ones with 318's had 7.25's a lot of the time, I know my '74 Dart parts car did.
But I have seen plenty of 8 3/4's. I have like 5 pickNpull yards within about 30 minutes of me though. I actually stopped pulling 8 3/4's because I have a bunch, couple of C-body 8 3/4's, a sweptline era truck 8 3/4 (for my satellite with an 8.25), and a couple of B-body 8 3/4's that I bought online and had shipped to me. Neither of those cost more than $250, even bought online and shipped. So, you don't necessarily need to find one local as long as you're willing to use a B-body housing.
The 8.8's get used because they're strong enough, and Explorers of the right era are easy to find in most local salvage yards. So, you can get them cheap, they usually have decent gears (lots have the 3.73 and a limited slip), and they come with disk brakes. So you can't beat the price, I mean, I could get a complete 8.8 from pickNpull for under $200 most of the time. And if you can weld you can shorten them. But again, you don't even need to shorten them for a Demon if you don't mind running slightly higher offset wheels. So basically if you have some mechanical skills the 8.8 is a great way to cheaply install a rear end that won't blow up, has disk brakes already, and usually doesn't even need a gear change or limited slip added. If of course you can get over the Ford thing. :p