I've been getting all the misc parts degreased and ready for powder coating on our 67 rebuild..

The fuel tank had a fair amount of crud inside.. I've washed out with degreaser the best I can but there is still a bit of deposit (inc some rust)..

What would be the best way to remove (or minimise) the remaining deposit in the fuel tank? Or should I bother as I'm guessing most cars would have a bit..

Would some acid work? If so what type..

Put some chain, coarse washed gravel, or old nuts and bolts in it and shake it round and round and that will remove any scaly rust. Damo.

Sounds good

There is a product called POR 15 that I bought for my tank. It worked great. 3 part process that ends wit an epoxy membrane that seals the tank. Alternatively you can take it to a paint stripper that will strip the inside for about 40 dollars! Then you have to finish it off

Or go to bunnings and get rust convertor and rinse it off, read the instructions on the bottle! It works well with mine.