Its been said but:

Contact Tech Section at Welshpool and explain you want to fit a A15 (dont mention cams, carbies) into a 1200 ute. You dont have to mention the brakes if you dont want to, Tech section may just tell you the brakes need to be upgraded. Or tell them you have fitted 120y Brakes as these are direct swap and compatable to the 1200.

Tech section will approve your engine, swap and list what requirements it must meet. For example they will probally state that you need a catalytic convertor installed and the factory carbon canister setup for the 1200 installed.

They will state what the engineer needs to certify, sometimes tech section ask for a brake test, other times the engineer does it to ensure the brakes are adequate after calculating. To easily prove the brake upgrade is suitable.

I would consult the engineer prior to contacting Welshpool as my engineer done the application and only gave them the info they needed.

I used David at:
Automotive Investigation Services
6 Viewpointe Cove
Ballajura WA 6066