If Canadian Codes permit and the building service is ungrounded 600V 3-wire, it may be possible to assemble a zig-zag grounding autotransformer to provide a neutral for the 347V fixtures. Three drytype transformers rated 240 x 480 Volts–120/240 Volts would be OK for up to 360V ø-n. [Alternate rating 120 x 240 Volts – 120/240 Volts]
The arrangement for operating 277V lighting on a 480V ungrounded service is described in: www.ecmweb.com/ar/electric_unconventional_transformer_connections
In this case, three 1½KVA transfomers permitted 18.75A/ø.
Clyde — What is the namplate current on the sixty 347V fixtures?
[If you like, I can post a typical interconnection diagram when the local server is back up.]