the majority of modern BP revolvers are pretty consistent in chamber diameter
of around .446 to .449.
So yes the Lee mould .450 and 200 grn will seal it. I use it myself.
However, I would recommend filling the grease grooves with a lube of your choice.
Many people make their own of beeswax and tallow (lard) cooking oil.
I prefer to be tradional in lube and use what they realistically had back then.
Paraffin was distilled in the 1830's but how common was it I don't know.
Olive oil was common in Spain and Italy but how common was it over here?
And yes some revolvers the loading area is not large enough to allow the use of conicals.
But if you are not adverse to doing it, a dremel, a small round file and emery cloth, you can open it up enough to allow using them. Then just reblue the area.
I did it to all of mine for versatility in what I have available.