I just posed this question to the guys over at Special Interest Arms (makers of the .45 ACP Enfield conversion mentioned earlier), and they had this to say:
"Sean,
Probably not practical from a time and return standpoint.
It would require many hours (days) to perfect, in addition to donor rifles, chamber reamer, head-space gauges, and other components.
Divided by how many buyers, at what price?
We get request for all sorts of conversions, no one ever seems willing to contribute funds or materials to upfront cost.
Show me a certainty of a decent return and we will be happy to pursue it."
I think this would make one heckuva decent target platform, and I would love to see it made. Anyone for drumming up some interest?