Rovertech (Matt) You deffintly need to purge the old gas from the system. The easiest way to accomplish what you want is to add a clean source of gas, add a 5 gallon can to the pick up side of the fuel pump (bypassing the old fuel in thetank/system). Disconnect to fuel line from the carb, unplug the coil (you don't want the engine to start just yet) and turn the engine over until you have fresh gas at the carb.
If you can remove the carb and drain the stale fuel and rinse the fuel bowl out with either carb cleaner or fresh gas. Once you have everything cleaned up you can remount the carb and fuel line, be sure to prime the system and check for leaks. If your good and have no leaks you should be able to turn the engine over enough to develop oil pressure. If you have oil pressure reconnect the coil and try to and start the engine using the 5 gallon can as the fuel source.
You may find you have other fuel leaks as the cab gaskets have probably dried out. I would be normal to have lifters tapping once the engine starts, that should go away as the lifter get primed again. I wouldn't worry to much about running the engine very long, the point here is to see "If " it will run.
Keep us up-dated on your progress.
NOTE: In a previous post you mentioned turning it over by hand and hearing compression, I believe the valves are opening and closing correctly.
