Mercury is the same as Ford for your purposes.

You said you have good spark but is that at the plugs? New plugs?

Do you have gas in the carb? Look down the carb and move the throttle linkage. You should see a healthy squirt of fuel from the spray bars.

You didn't say if you cleaned the fuel system from tank to carb?? That's usually the major problem in getting one of these to run.

When all else fails: I've found that it's often necessary to tow-start a truck/car that's been sitting for awhile. Find a quiet back road and tow it in high gear with the key on and they usually take off. The more you run them the smoother they get.