I tried remflex , copper,the old plain gasket type & so far the aluminum ones have been in there a long time & still good.
I found a couple pair of "dead soft" aluminum ones from Summit in my collector parts box this afternoon. Never run them before... IIRC I was using Mr. Gasket Ultra Seals the last time.
This is an existing TTI system, so no conversion to gasket-less joints w/ v-bands. However, I'm adding a second set of collector hookups between the mufflers and the tail pipes so I can drop the exhaust between the headers and the tail pipes to make trans maintenance (primarily) easier.
I'm also changing the collector config from the headers to use Flowmaster 3.50" to 3.0" tapered collector extensions, instead of the standard short TTI 3.5" to 3.0" collector reducer. It might not make a noticeable difference, but we saw some loss of torque when a straight 3.5" x 18" collector extension was tested vs a standard short 3.5 to 3.0 collector reducer with an 3.0" x 18" collector extension. Torque curve comparison attached below.