I need to replace the outlets in my 54 y/o home but the junction boxes are too small to accommodate the new outlets. Is there a way to replace the junction boxes without having to cut a new hole?
First, you do not need to use GFCI receptacles at all. GFCI is not a receptacle, it is a protective filter. It can be placed anywhere along the feed to the receptacles. It can protect every receptacle that is downline of it.
They make GFCI circuit breakers, which obviously protect the whole circuit. They also make GFCI bare modules, which resemble a GFCI receptacle but with no sockets.
Regardless, a circuit is typically wired in a string or sometimes a tree. A GFCI receptacle can be wired to protect every outlet downline. So if you have 6 receptacles in a circuit, you only need one GFCI and it can be wired to protect the rest. That's why they give you a bunch of "GFCI Protected" and "No Equipment Ground" stickers in the box, those are for the downline outlets!
In fact, the way most people wire the GFCI when they're not paying attention, ends up protecting all the downline outlets even though they don't intend that. Hilarity often ensues.
A secret trick to install GFCI in too-shallow boxes is to fit what's called a "surface conduit starter box". This sticks out about an inch proud of the wall surface. It's actually intended to then attach surface conduit to the sides of it, but if you don't install any, I won't tell :)
Let me guess: the wall boxes are metal and the "ears" on the new receptacles are hitting the wall around the boxes, right?
The "ears" are scored to allow them to be broken off leaving small tabs with holes in them for the screws into the boxes. Just grip the ears with pliers and bend back and forth. In some designs the ends of the center tabs are also scored for breaking off to allow fitting into the tightest space.
The ears have holes in them to allow them to be used as shim spacers to stand the receptacle out if the box is too far into the wall. The use of metal shims makes electrical contact of the ground of the receptacle with a metal box. Some receptacles have a paper "keeper" on one of the mounting screws and a metal keeper on the other end. This provides metal to metal contact on the end with the metal keeper. If you are using cheaper receptacles with paper keepers on both ends, remove at least one of the paper keepers to insure metal to metal "face" contact for the ground.
But you would be advised to use a better grade of receptacle. And I assume you are using the now code required "tamper resistant" receptacles, right?
Does your home have aluminum wires or copper wires?