2003 Ford F150 4.6L: Leaking Plugs Question?

This is known as frost plugs and you should not have to lift the motor to change these plugs

Those are called freeze plugs. They protect the engine block from cracking if the coolant in the water jackets freezes. The plugs are designed to pop out to relieve the pressure generated by the expanding frozen water. Two of my freeze plugs rusted through and were leaking like yours are doing. But in our area, we have a "Mom & Pop" auto repair garage near-by. I took my 1990 F150 there a few years ago and had them replace all of my freeze plugs to brass ones so that they would no longer rust out. It was a lot easier than trying to do it myself!

Using rubber "test plugs" for any extended amount of time would really get you stuck on the side of the road. Since heat of the engine would make the rubber soft and the antifreeze would help reduce the grabbing friction of the plug so that it will eventually pop out and leave you stuck somewhere with no coolant at all!

My suggestion is to try and find a local garage.

Rent an engine hoist and hook the chain to the lifting loops on the engine.

I don't know who makes them but you can get a rubber plug to go in the hole.  It has a stud and nut in the middle to compress the plug to make it stay put and seal.  I used one on a car where there was no way to hammer a new freeze plug in without removing the engine.  I could puncture the leaking plug and pry it out, but I had no room to pound the new one in.  I bought it at a NAPA store.    

P.S.  My rubber ones lasted for many years