IT'S A 454 Cassul...
yes you can shoot "Ruger only" 45 Colt loads in your gun... so long as the pressure is lower than normal 454 Casull pressures... ( which are insanely high )
I'm not a Taurus hater, I have a TCP on my belt right now, & 2 revolvers at home I used as bases for custom guns...
but I honestly don't understand the use of the Magnum Judge, other than to use up parts... ( a regular Judge, used as a short handy .410, could be a great skunk gun for the truck ) but a 454 Casull with the huge bullet jump, at those insanely high pressures, just doesn't seem like it would be what I could find any use for, & same would go for hotter than SAAMI spec 45 Colt loads...
if the OP doesn't mind, what do you plan to use the gun for??? ( if you tell me just for fun, I'm totally fine with that ) but if it's for anything that is going to involve saving your bacon from danger ( 2 or 4 legged variety ) I just don't see it as money well spent...