One other thing...I would drain all water out of it. That water will act as a heat sink and cause you to use more heat to braze or solder than is necessary. After 10 years there should not be any flammable things left there. And another point: you can use J-B Weld to fill those holes if you wish. Use the regular formula and not the Kwik-Weld formula. The company (around for about 50 years now) says once it is cured it is resistant to all fuels. In fact I used it diluted with acetone to paint the inside of a gas tank on a log splitter and it worked just fine.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end