Justin,
Sorry to disappoint you. The other guys were going at it pretty good, and they have a lot of experience. I'm fairly luke warm on frame swaps, for many of the reasons implied in Sub's post. Most I've seen (and I've never done one) end up looking pretty crude. Again, I would qualify that by saying that a very skilled individual stands a better chance of making one look like "it belongs" by applying his skill. I guess most I've seen are from folks who lack both funds, and sufficient skill. That being said, I have seen a couple of successful swaps on '49-51 Mercs over mid '70's GM chassis. In these swaps, both the frame and the entire floor pan, firewall to trunk, have been used. The floor (or what's left of it) was cut out of the Merc and the body shell dropped over the trimmed GM. A little channeling was done, so the body sat closer to the ground, but the suspension had full travel. The builder had good skills, and integrated the inner fenders, under the hood, well enough that it looked pretty "natural". Welding in a full floor is a big job, but with good set up and "shoring" during the job, a conscientious worker with decent skills should be able to pull it off. Depending on the dimensions of your car, maybe a mid-size car, e.g. a Malibu would be more appropriate. Some time with a tape measure and a couple hours roaming a Pik-a-part might give you the info you need.

I don't recall what you mean by your frame being near death. Are the rails rusted through, or was in such a brutal accident that it's beyond straightening? Just asking because if the basic rails are good and you just want to shed a failing suspension system, there are a number of options there that could be a lot easier, and less likely to cause ugly compromise.