Yeah, My 68 had a styro bottom. but cutting into it for an access panel would have to take a lot of care without taking it off. You wouldn't want to slip and cut the tank. But if you are carful an angel grinder could get the job done.. IF YOU ARE VERY VERY Carful.. maybe set up a stop so you only go so deep.....
May you have at least one sunny day, and a soft chair to sit in..
2008 5.7 L V8 Sequoia
AIR # 31243
WBCCI # 6987
FOUR CORNERS UNIT