Striped Threads in aluminum housing

[Second Series]

I have a 1988 GMC K2500 with the 5-speed transmission. My knuckles hit the dash when I shift to 1st and 3rd. I unscrewed the dust boot to find the top bolts loose. It was leaking there when I got it so I put two longer screws in, I thought it would work, but no, Two of the Four bolt holes the threads in the aluminum housing are striped. The bolts are M6 x 1 x 25. Does anyone have a suggestion for a replacement bolt? Maybe a self tapping bolt that’s slightly larger?