A quick update. According to the people at POR their "Prep and Ready" acid treatment is safe to use on Aluminum tanks when used as directed (e.g., don't let it soak inside the tank). The did recommend using their "Marine Clean" to prior to the prep and ready to remove residue for the decayed rubbber bushing that held the fuel pump. I had the POR 15 kit and ordered a quart of Marine Clean for $15 delivered.

I also checked the web site of a local shop, Looper Service, that I used before to repair a bike radiator. I haven't contacted them about the tank yet--I want to try my own repair first.

As a back-up I found a K75 tank in Upstate NY on Craigslist and my brother checked it out and picked it up for me. I'll be driving up and seeing him this weekend.