Is that a snubby with the 2" barrel? I think that's the only ones they made with the bobbed hammer.
It's not much work to put a regular hammer in but I'm not sure why you'd want to if it's a snubby. They aren't good for much but self defense and you really don't want to use single action in defensive scenarios...too much potential for losing an "accidental shooting" lawsuit even if the shooting was intentional and justified...
I'd spend the money for a good action job instead so the DA pull is smoother and lighter...
Just my $0.02, of course,
John