Slant 6 intake/exhaust manifold bolts

I think the two small ones are 5/16, I got those at Ace, but had to cut the threads longer. The 3/8 one is a stud with a washer nut on top. I think I cut the head off a bolt and threaded it to make that one. Your manifold probably came with 3/8 for the exhaust flange. I drilled and tapped those to 7/16 as my originals were. Got studs on eBay for those. All grade 8 , figured if they are a little harder I have half a chance of removing without breaking if they get seized in.