dump valve on '67 Safari

[JRF0st3r]

I've removed the dump valve after being unable to stop leaking at the gate by cleaning out the groove with my toothbrush. Removal should facilitate subfloor replacement. I'm thinking that a new valve, probably AS part 08706, would be more likely to perform longer than just replacing gaskets. Removal of the valve was challenging because the lower two nuts were corroded and access was limited. Finally I cut off these bolts, which may have been a major mistake. Were these bolts part of the outlet permanently adhered to the tank or a part that can be removed and bolts replaced? See photos. Hmmm, maybe a bolt stretcher...
Advice?
Jim

[JRF0st3r]

Problem probably solved. I removed the BW tank and found that I could back out the bottom bolts just enough to cut off the heads that some person had installed backward. Than I unscrewed the rest of the bolts.
Now I need to reinforce the plastic surrounding the heads. Do you have recommendations?
Thanks,
Jim