Plan C would be the most expedient with little to no sacrifice or supporting modification, and you get the weight loss benefit.
Plan B1 is realistic as well in that it's a drop in proposition IF you snag as much as you can off the doner car - fuel lines, vacuum lines, cables then it's as simple as modding the wiring and getting a tune. The main issue will be exhaust depending on what your plans are there. Because Marks use an integrated cat/manifold on the driver side, if you have stock piping, you'd want the whole midpipe assembly, which from the midpoint back will mate to a factory Tbird exhaust, problem though junkyards tend to cut cats off before they hit the yard, which serves as a double whammy if you want to use the whole front section or just the manifolds/cats from it. Only other option at that point are Kooks and all of a sudden this is a $1,000+ engine.
Plan B2, while it sounds fun has a lot of holes, on top of needing cams, needing valve reliefs, you'll also need springs, and don't forget about the supporting stuff like new head gaskets/bolts, cam degreeing stuff, tune, ect. And power wise in the end you're going to be limited by the stock heads and intake, it'll just be a hot PI motor, and for the time and money it just isn't there. IMO that whole recession buster setup isn't much of one unless you work at a junkyard and get freebies, have all the right tools to do it all correctly, and have a machine shop and the ability to port heads at your disposal