Im THINKING (which can be dangerous) that if you go to any trusted source of reloading data, you could use loads for any 500 grain convential bullet (cup and core) bullet of that shape (500 gr RN) and be ok. (If im wrong on that please tell me, id like to know).
Also, having had direct experience w the 378 weatherby, i bet if you start extra low with loading (like 20% down on powder where safe) and work upwards in loading, unless youre a recoil junky, your body will max out on fun before you max out on pressure
There might be 458 lott level load (2400 fps w 500) that would give awesome terminal performance (noticeably better than 458 win... many have thought 2400 was a "magic" speed for game performance, look at 458 lott, 450 rigby, 416 rigby, etc), have low pressures, noticeably less recoil then top end loads, and give great case life. From my experience wthe 378 weatherby (and 338-378 too), norma (who made a lot of the factory 378 based cases) brass is on softer side, starts showing pressure signs early (like at 65k loads starting to look like its 75-80k in other brass, with ejector marks and such). I think of "full power" 460 wby in full size barrel (24 to 26") as being 500 gr at 2600 to 2700 fps.
oh, one last thing, if using factory weatherby rifle / chamber, it usually has a very long throat / freebore, gives bullet long jump to rifling, allows more powder / velocity w same pressures. That jump could be .500", .750" long...If you have a more conventional chamber (where bullet has short jump to rifling), youll def want to start low and workup, most of the load data out there will be for the factory long-freebore weatherby chamber. Note - out of curiosity i went and looked up chamber specs, and it looks like weatherby has shortened its freebore from .975" (superlong) to .756" (still decently long). Where your actual freebore is will play into loading for your rifle... shorter freebore = less max powder, all else being equal.
Btw, what i recommended about downloading was to point it out as possibility, if youre one of the people that loves to max everything out, more power to you, not knocking it
Ive done plenty of things like that in my own life in various ways. Good luck, have fun, report back