led-panzer's 1984 300D 4-speed
led-panzer's 1984 300D 4-speed
Welding AL to be airtight it a little trickier than just welding it for structure. Doing thin AL might be a PITA too, with respect to burn-through.
If you can get a slip fit, I would braze. It just wicks right in there like solder. Some of the AL brazing rods on the market today are pretty badass.
Other than that, why bother? Your setup looks good. Nice work. Do the pipes have beads to grab the silicone? If not, send 'em to someone with a bead roller. It's good insurance.