i fitted plastic
You probably have heard of CAK tanks.
They can supply a variety of 'off the shelf' plastic tanks with all fittings.
We mounted a 120 litre tank inside vehicle above rear axle and it is now hidden behind worktop.
I then like the idea of more standard items (in case replacements needed in far off places !) so I fitted ordinary low price house hold tap, an inline pump and seperate inline pressure control (flow switch) to operate.
Has been fitted and working fine for last 2 years and 29000kms (including a roll in Mongolia).