it's a 283 [Taskmaster, Trademaster, or Super Taskmaster], the 265 wasn't used in any series '57 CDN trucks according to the '57 Canadian Owners Manual I have .... I doubt GM had totally different casting numbers USA vs CDN regardless which plant cast the parts .... in David Vizards small block book heads 3731556 are listed as '57 truck, block casting 3731548 as 57 truck - heads and block 1 year only
Bill
