There is nothing special about the 496. Find a low mileage used engine out of a gm truck, throw in your cam, freshen it up, thoroughly clean and inspect ALL of your auxiliary components and then swap them onto the longblock...easy peasy. Pay attention to injectors, rails and other fuel components.

Does the engine sound like spoons in a blender or does it run poorly? The 496 has a habit of eating pistons but if you are lucky you just burned a hole in one. If there is no mechanical damage, you can have it rebuilt with forged pistons, then just have the heads done and you are back in the water.

There are several places that do 496/8.1 short and long blocks. Even a low budget mechanic can swap the accessories to a long block.

its all the outside stuff that is expensive from the OEM that is special to the long block - also the early 496's cam sensor can be an issue

the GEN 3 cool fuel is expensive for the years it was installed

PCM 555 controller is expensive

cooling systems and those parts are expensive

Exhaust system is expensive.