So I recon you've got two choices on which vehicle this really is,
original chassis was 4x4 126 this was 170-128 and then had a chassis swap to 4x4 427,REMLR database says
170-128 1964 - Mk.3 6069B Truck, Cargo, 2 1/2 Ton, GS, With Winch AGD282.9683 427 - 12.00x20 NSW. original engine 8227
Original chassis 126 replaced with 427
1 Coy RAASC , Vietnam Convoy Orders 18/6/66. Packet No.2, 1 ATF 08.03.1977
I can't find which ARN originally has 427 chassis
What is the engine number of the truck you bought?
New chassis is 4x4 328 - interesting the RAEME workshop plate has the ARN for the new chassis - so this vehicle maintained the ARN of the chassis - so 170-411 is the chassis and the body is 170-128
usually (but not always) the ARN stays with the vehicle (body) as the chassis is just another part....
so obviously you have a combination of two vehicles - both where in SVN
I think it correct that it is 170-411, as stated on the RAEME workshop plate