Stripped bolt in valve cover. Best way to fix?

[Freddo]

Hi everyone! Got a quick question on the best way to deal with a stripped bolt in my valve cover. It's a 1967 283 with Mickey Thompson valve covers which appear to be aluminum. These were on the truck when I bought it 1 1/2 years ago. The bolt holes on the valve covers are raised and it appears that some slightly longer bolts than stock were used and even though they are longer, these longer bolts don't appear to get a lot of threads into the hole. These valve covers have been leaking since I bought the truck and after reading the threads, put on a felpro neoprene gasket with the steel which sounded like the best bet for stopping leaks. I got everything changed and as I was tightening down the lower front bolt on the passenger side, I stripped it. It wasn't very tight, so it might have been already stripped. I pulled the bolt out and the threads look thicker on the bolt about half way down it, but it doesn't appear to be cross threaded.
Bolt length is about 1 1/4 inches & it has a 7/16 inch head. I was planning to go down to parts store & buy a slightly longer bolt to try to get it past the bunged up threads in the head. I don't have a tap or other tools to clean up messed up threads & haven't used one before but would be willing to buy one (if not too painful) and learn. What would be the least expensive and/or most effective way to fix this so that it holds the bolt? All help appreciated!