The Mk 1 is going for $125 on up, depending on condition, and sells well. They shoot pretty good, and they have some aftermarket parts support.
The 38C... $85-$100...maybe. There are some things that will drive the value up on them, the earlier ones are worth a bit more, they have brass valve bodies, and the hammer acts directly on the valve. If that is what you got, you could be up on the price range..or not.
The 454...~$40-50...maybe.
Check out the forum as per above. They have a pretty active crowd, and the buy and sell forum there has enough listings that you should get a good idea of price point for the 38C and the 454.
Cheers
Trev