I've restored several tanks. The kits work but sometimes yoou need to do a little assist. If the rust buildup in the tank is a lot, dump some roofing tacks in it and vigorously shake them with some stong cleaner to dislodge the loose stuff. Once you get clean water from this procedure, go with the rest of the kit's directions. The real key to these kits is the rubber lining.
Spook, I had the tank for my 48 Chevy cleaned out at a radiator shop at a cost of $110. For me it was well worth the cost because I didn't have to do the nasty heavy work. it came out just like a brand new tank.