I am a medicore welder at best. I have welded aluminum successfully with oxy acetylene. I have used the Henrob/Cobra type torch, although torch type isn't especially critical. It does help to get ther pressure down so you don't blow the puddle all over the place. The bigest limit to gas welding aluminum is operator skill, it take a touch to keep the heat just right.
This guy is the "savant" of gas welding aluminum. https://www.tinmantech.com/index.php
When my buddy bought the Henrob torch at the flea market at Mid-Ohio, I though oh yea, there is always have one of those "savants" at events that seems to be able to weld anything with anything. We set up the torch, I watched the DVD and I tried it. My two coupons stuck together. They weren't perfect, but they stuck.
Even with a month of practice I would consider trying to weld that fork leg.