The Marlin action can't handle 50,000psi .45-70 loads, much less the .454's +90,000psi proof loads. What folks don't seem to understand is that all the manufacturers and several custom gunsmiths tried to adapt all the existing actions to the .454 over 20yrs ago when Ruger brought the cartridge into the mainstream. None succeeded, especially the Marlins. The Winchester Big Bore 94 did okay at 50,000psi and Keith DeHart built a few. The 1892 does the best of the pistol length actions and the 1886 handled it with ease but no one wants a 9lb .454. It's the large vertical locking lugs that make the most difference. That is why the only commercially available levergun in .460/.500S&W is the Bighorn Armory, which is an 1886/1892 hybrid. Basically an 1886 abbreviated for length.
Maybe the incorporation of stronger alloys like Ruger uses in their .454 revolvers would help, maybe not.