Hot Rods 392 Hemi block cleaning

I am about to clean a 392 hemi block of all the internal water jacket rust prior to Moroso block filling. My question is -
Has anyone used OXALIC ACID to clean a early hemi block of all the rust in the water jackets? If so please can you advise the ratio acid to water and approx time scale.
I intend to fully submurge the block in the liquid.
thanks

 

Dipping, washing, rinsing, tanking aren’t as good as some physical agitation/abraded via brushes and wires in all the holes thru freeze plugs around cylinder walls in all the nooks and crannies while being flushed with water.
Then tank it after the scraping