manifold bolts/washers

The studs in the head are probably an Ace Hardware item, though I would look for better Grade 8 studs. They might interchange with V-8 studs. I am guessing you are mixing up terms and really need only the washers (nuts at any hardware). There is a great write-up on www.slantsix.org (can find links here). The outer exhaust studs have thick round washers. You install the triangle washers with the bulge away from head (I recall). If you don't do it right, the exhaust manifold can crack.

As far as where to buy the washers, I don't know. Seems I have seen them though. Check the dealer since slant engines were used into the mid-80's on trucks and vans. One co-worker in the 90's bought all new ones for his Dodge truck at the dealer since his manual said to not re-use the washers. First time I ever heard that, and I expect most people here re-use them, but it does suggest dealers would have stocked them.