Charles Mellon makes valves, flat top pistons, pump arm goodies, all sorts of stuff. All very reasonably priced, valve and flat top piston is 30 bucks for example. Build your own back packer. I can make you up the part for a stock quick disconnect. You can get a longer .22 barrel from crosman or ebay. Charles may still do .22 barrels.
I have a pistol that I bought from another member and a carbine I did. Lots of Mellon parts in both, they shoot a lot harder than a stock gun. Alchemy air works on ebay sells a lot of Crosman parts. I bought a 177 Barrel from him, great quality inside and out.
1377 pump piston, 1377 pistol valve
mellonair.myfreesites.net