Stripped Threads

Finally getting ready to finish the rebuild on my KZ1000 M1 and want to address a problem that's been present ever since I bought the bike. The four outboard valve cover bolts that go through the rubber inserts were stripped by PO preventing a decent torque-down. Two bolts would sorta tighten down, but if I torqued any harder, I know they would completely strip. The other two were outright stripped. What I did was buy longer bolts and tighten down using nuts underneath the valve cover. but that was temporary as I would always get oil seepage at the bottoms by the nuts and around the bolt heads on top.

So now I want to permanently fix this issue before installing the engine back in the frame. I have read on the forum that Time-Serts seem preferred, but there is very little aluminum around this area, and I was wondering if any of you guys have ever done this, and if so, did you use Time-Serts? Appreciate your guidance!