How many header bolts are needed?

[32valvesftw]

So..I Had headers made and installed, partly cause I was chasing leaks and partly cause I wanted better performance. I definitely got the increase in performance but I always thought I had some type of exhaust leak as I always smelled exhaust in the cabin if I sat at light or in the driveway. Today I put the car up on ramps today and noticed three header bolts that were backed out at least 3 turns each, and 8 bolts missing from the passenger side. The drivers side had a few more bolts but also had loose ones. I tightened what I could and hopefully can order some new ones to replace the missing ones.
Now I know some of these are hard to get to to, but I am talking about the bolts I can touch or see with the car on ramps in my driveway.
I want as many bolts as possible installed, so do the stock bolts back out from vibration, do I need a high temp locktite? Anyone had similar issues? the bolts are steel and the heads are aluminum so I would think galling and seizing would be a bigger issue than backing out.