Patchy, I love your sig!!
As for as swapping frame and such, a stock frame will fit and work better and look nicer than anything else.
If you can't find a stock '55-59 chassis for your truck locally, you're not looking hard enough. I know of at least two in local fields, I see rolling chassis on my local Craigslist for anywhere between $50 and $500 dollars. Sometimes I see complete 55-59 parts trucks on there for cheap, too!
Buy a running 70's Chevy 4x4 for $1000, part it out for some beer money, and use the drivetrain, axles, tires, etc, etc in the '59.
It's so easy they practically sell 'em in Betty Crocker boxes, just add water and bake!!
That being said, the flip side, metal is your *****, you can do anything with a welder and time, but how much time and effort to do you want to put into that?
Your new frame will need new cab, radiator, and possibly bed supports welded on to mate to the old truck, and it's quite likely the floorpan may need to be altered to fit your "new" frame.
Don't forget about all the details, stuff like bumper mounts, moving the master cylinder, hanging pedal assembly, possibly clearancing/recessing the firewall and making a transmission tunnel, along with lots of other stuff. Might not be a problem with a Task Force, but sometimes the frame hangs down lower under the truck, and it looks like total ***.
Your results may vary. It is your time and money, but I pose the arguement for stock frame, 70's running gear.
