The problem with finding one of the big old torquey saws like the 090 and 076 is that they've been out of production nearly 30 years, and there's a collector premium on them now. Even in the "big wood days" not everyone was packing one of those pigs around (back then the 056 was king).
Nowadays for serious chainsaw milling, the go to powerheads are the 880 Stihl and 3120 Husky, with some going with the 660 Stihl or 395 Husky. I wouldn't bother with anything under 90 CC or so, need that power for ripping.
I've seen some 880 "clone" saws (built from chicom aftermarket parts) for around $1000, but kind of suspicious about long term reliability (we never used aftermarket parts when I worked for a saw shop, lots of problems with quality control).