Trans pan gasket..sealer or no sealer?? and other trans ???

Cometic makes a gasket that is slightly thicker than stock, they seal great (assuming your pan is flat), and you can resuse them multiple times if necessary.

In my Torqflites I've always used Dextron/Mercon and never had any issues. As noted earlier, Type F is what we used many years ago, but of the guys I know that build transmissions they say avoid Type F and use D/M.

S