Obviously, this can be done, since Ford had 69 and 70 cars with fat blocks in them. However, it is not necessarily cheap or easy. These are the things you'll have to consider, IMO.
* Shock tower modification. Ford had this done by a contractor to cars that were shipped before the engine was installed. I believe there are kits made for this modification.
* Heavier Springs - These engines weigh quite a bit, and if your car was originally equipped with a small block, you gotta do it.
* Bigger front swaybar - See above.
* Good brakes - Disc brakes (and good ones) are what it's gonna take to make a car with this kind of additional weight over the front wheels stop safely.
* Beefed up cooling. Big motors make lotsa heat. Plan on a larger, more efficient (4-row, maybe aluminum) radiator upgrade.
* Exhaust modifications. You'll have to clear those shock towers with that motor wedged in there. Count on headers made for this application and a custom system behind them.
* Driveline upgrades. A smallblock C4 can handle big torque, but not without a serious build up. A C6 would be better. A big-block toploader or a Tremec will do the job, too. A 4-spider, 9-inch rear will also be required,unless you plan on driving like a little old lady.
I've not done the conversion, but know a couple of people who have. It is a very neat upgrade, and sure to get alot of oooos and ahhhs when you open the hood. But it is not a cheap one.
Let us know how you intend to move on this project and send pictures when you get it done!