Transmmision 89 6 cyl 2.8 auto trans

What kind of gasket do you recommened rubber or cork and should I use a gasket sealent? If so what type I had to drop this thing 3 times all ready it doesnt have a drain pulg so its a bitch im getting to good at changing this thing except it wont leak for a while then starts leaking every time I had a rubber gasket in it when I changed the filter but I broke a bolt off and I carried it to a trans shop to get the bolt drilled out they told me to use cork well they had a cork on it and it started leaking again the bolt they put in tightens up too so I dont thinkk thats it the bolt wernt tight when I checked them so I tryed to snug them worked for a short time so I dropped the pan again and put black sealent on it worked for a little while but not to long should I replace the pan too it has been scraped on something/ it has a road rash on it /it scraped on the corner tired of this thing leaking and the money I put in the fluid I put the good stuff in it cost 10.00 a bottle to add it to the fluid and I try to get the additive in the fluid like slick 50 or what ever it was lucis etc thanks for any help this is getting to exspensive and im scared it going to mess up my trans