Brass tanks will be all brass copper construction. There may be exceptions. I have not seen any aluminum & brass radiators.
Plastic tanks will generally be aluminum core but there are copper plastic out there.


With a factory Montero radiator you should be safe with Muriatic.


Cheers, Charlie
If It ain't broke, Modify it!
87 Montero turbo Converted back in Spring1989
95 Montero SR 3.8 DOHC Only one?
93 Pajero 3 door 6G75 Mivec with paddle shifted 5 speed
Then a Gen2 SR with full coil independent suspension.