I'd say go with a western frame off ebay- they are pulling them now ahead of time, so you can see what you are getting...I was afraid to buy one sight unseen back in '03, and shipping halfway across the country woulda cost as much as the frame- so patched ours(actually only saved 3' of the front and the rear crossmember). Sad to say, but most of these frames rotted from the inside out, and from what I saw of ours, everything that was 'low' was gone...the bottom of the front rails to halfway up the rear arches- worse yet the torque boxes were gone. If I had to do it again, Id go with the ebay/arizona frame in a heartbeat.
I have never seen a frame repaired 'in the car' that was more than a temporary fix- you really need to drop it to be able to clean/weld properly, if going that far, might as well go the extra 25% of work to swap it out. expect to replace all the bushings, lines, etc, plus the rocker tunnel will likely need some repairs once the frame is dropped.
theres a bunch of pictures of ours at saving a 65 galaxie