Wow, I would not ride it like that.
The brittle nature of aluminum makes it prone to catastrophic failure with little notice, unlike steel.
Find a good tig welder and consult with them. Maybe look for a race car frame builder? they are more common than you might think.
A good grind and fill can be very strong and last but experienced eyes on the job is important.
1991 MariStar 240sc, 454, tower, WetSounds, Krypt and Rockford Fosgate