My car with engine in it sat for between 5-10 yrs before I removed and disassembled the engine (I removed it in order to check the VIN stamp on the block - which had bothered me for years because it had no vin on the machined block surface). After I found the VIN stamping, I went ahead and disassembled the block (for one day rebuilding). I still haven't decided the smartest way to rebuild the 302 engine and it's still apart. I have a '70 LT1 engine which I rebuilt which has sat in the car for years without it's being started either.
2 or 3 yrs ago, I began cleaning up the car, disassembling where I needed to in order to rebuild/check/clean the parts and then reinstalling. I'm down to the front clip parts (it's an RS which is a monster in itself).. and the dash components. At this point, I'm not sure if I'll leave the 350 in it for checking everything initially, or if I will rebuild the 302 to stock specs (I had 12:1 pistons in it from the '70's).
Re your engine, if it was running when it was parked and it's been parked in a garage, then I'd think you aren't too bad off and your engine will be fairly easy to get running again. I'd suggest the following:
1) your carburetor is going to need a cleaning and kit due to dried out fuel and gaskets.
2) your fuel tank should be drained, cleaned, checked for leaks along with your fuel lines.
3) pull your plugs and squirt some thin oil or auto trans fluid in the cylinder; I'd do this a few times over a few weeks period before I tried to start the engine.
4) pull the valve covers, squirt oil in the rockers/balls area and on/around the pushrods/lifters if you can get oil to them. check lash if you need to do so at this time. reinstall valve covers.
5) with the ignition coil disconnected, plugs still out, make sure your battery is charged and do some short spins of the starter motor. Don't spin it too long each time, rest/cool it, but continue doing that until you can see the oil pressure gauge begin to register. I would disconnect the fuel line from the fuel pump to the carb during these spins; you can put a short rubber hose to the fuel pump outlet and drop it into a gas container which will allow you to purge any old gas our of the pump, and verify the pump is pumping.
6) Check your cooling system, verify your water pump is working while you're spinning the motor, then drain the cooling system and fill with fresh water and a little coolant.
At this point, with your carb rebuilt, your gas tank cleaned and with fresh prem fuel in the tank, plugs cleaned and reinstalled, you could try starting the engine. Note: if you need to check timing, you can verify static timing prior to starting the engine - it's simple to do.
Assuming the engine starts and runs OK, good oil pressure, and maintaining coolant temp (make sure it doesn't run hot for any reason), let it run til it reaches normal temp, then you could cut it off and drain the oil while hot, and refill with good fresh oil.
Note: Do not drive the car before you check the brakes and any other system you have reason to suspect.. I try to make sure that a car will STOP, before verifying it will drive..