Probably not what you want to hear but...
As long as you have an original that's reasonably straight and doesn't leak, it'll probably be more cost-effective to just have it rechromed. Best, wild-assed, guess $300-400 for triple chrome at a good custom shop. Alternatively, you might source a painted version of the `86 tank...if one exists...and have it chromed. Those original `86 RD tanks are rarely seen for sale.