Hush07: From my own experience, bullets cast from wheel weight lead or other harder alloy, generally drop from Lee molds about 1-2 thou. oversize (.002" seems the norm). Have no direct experience with the 379-250 mold. But have observed the same with other bullets I've cast.
So... you can expect that bullets from the 379-250 mold should drop around .380-.381". In which case, you can likely lube and load them as cast, without sizing. Depending of course, if your rifle's chamber throat will accept that bullet diameter. It should, but bears mentioning.
If a custom mold seems a better option, I've had good experience with Accurate molds. These can be cut to any band diameter you choose. So offer plenty of latitude. Other mold makers out there too. This being only one of several.
Since Lee molds are inexpensive, I'd be tempted to take that route first, though.
Al