I have used white silicone for wing fillets with no troubles. Your fuel line is silicone. If you are wanting to seal the larger holes, and if you have to remove the tank, it will come out anyway, just use regular silicone caulk. It's not like you are going to pour it over it all the time. You probably have some of it on hand. If you buy the Permatex product, use just a few dabs, the rest may go bad before you need it again. Being resistant to gasoline is different that alcohol also. It may be resistant to gas, but NOT to alcohol . You could take a piece of this plastic like credit card stock, drill some nice fitting holes in that to match your tank plumbing, and glue that in place with the clear silicone and create a better seal and use less silicone. And if you ever need to remove it, you will be able to do that also.
Good luck with it,
Dan McEntee