Cleaning Out XJ6 Fuel Tank Rust

I've got one of the rusty, gunky, fuel tanks out of my 1983 SIII
XJ6 that I'm trying to get back on the road. The car runs from the
other tank, but the pre-pump filter I fitted blocks up with rust
after a few minutes running, so I've got to to clean that tank
later as well. There aren't any businesses advertising fuel tank
repairs anywhere nearby that I can find, so cleaning them will need
to be a DIY job.

For removing the rust I can get some Sulfamic Acid for free (mixed
with Sodium Bisulfate). Phosphoric Acid seems more commonly used,
but Sulfamic Acid manufacturer websites say it works for rust
removal too (10-20% concentration). First I'll spin the tank on a
cement mixer with a chain inside to break off the big flakes of
rust, of which there look to be plenty.

The other option I'm considering is washing soda and a battery
charger for the electrolysis method of rust removal. I'm not sure
if that might be more or less likely to encourage fresh rust after
treatment? At the moment I'm thinking I won't use one of the tank
sealer products since it sounds like they can be a new source of
gunk in the fuel line, so I'm hoping I can seal the tank up and
won't immediately go rust again, as some say happens using Muriatic
acid.

Or the reproduction fuel tanks do look tempting. RockAuto seem
cheapest for them (inc. delivery to Australia). About $750 each.
I'll at least have a go at reclaiming the originals though.

-- 
OmberJag's Jags:
1990 4L Jaguar XJ40
1986 3.6L Jaguar XJ40 (parts car)
1983 4.2L Jaguar XJ6 SIII