Canada initially used the GPMG in 30-06, and these belt loaders were in their original configuration for that caliber. I actually got one that went to scrap out of Moose Jaw in the mid 90s. It had tags on it indicating it had been used at CFAD in Dundurn.
We had no need for them in .308 since those guns used the metallic links.
The conversion kits were available from Ohio Ordnance back when the M1919 craze was on in the US. Not sure if they still sell them.
I'll say this much about the TNW M1919s: They can be a bugger to get running smoothly, but once you have the bugs worked out, they are pretty much the most fun you can legally have in Canada while still wearing pants.