Post-war conversions: C15TA to Tippers?

[David_Hayward (RIP)]

I am intrigued by several CMPs listed as 'GMC' as 'make' registered in Oldham Borough Council in 1947. These were 3-ton [60 cwt] 'Tippers', and yet the chassis numbers are all 8 4449 etc. i.e. C15TA chassis! Does this make sense that the armoured truck chassis were rebuilt with say a new cab and new body? WD numbers quoted include '158367', '158361', '158371', '158319', '158277', '158343', '158285', but these do not tally with any known series unless these were Mid-East allocations. Anyone ever heard of C15TA trucks being allocated such Census Numbers?

For Morris fans, here's one for you:

EBU 105 Morris (ex WD) Chassis 7511 56 cwt lorry 18/8/47 'C8AT1961FWD' whatever that means!