wow that's a pretty tall order. I doubt there are any out there that are not on rifles. I would tend to agree with Bearhunter here, although Canada never used FTR marks, so unless it was done in Europe it won't have them. First as you are saying Long Branch '41 is it still in mk1 configuration? I would suggest the first think to look to to see if it was refurbed was it upgraded to mk1* and/or does it still have the round cocking piece? If either of those were done, it was more than likely FTR'd and a mk1* fore end would be correct.
Of course Long Branch and CA weren't really as particular as the Brit factories when it came to rebuilds, and there are NO absolutes. I have a matching factory '43 mk1* with original 5 groove bbl that still has most of the mk1 parts, and I took it out of the packing grease.