[blucar]

I don't recall there being anything special about the exhaust manifold bolts for a Y-block.
I would suggest ARP as a source for good high quality bolts. Victor/Macord use to make a very good gasket w/heat shield for the rams horn type of exhaust manifolds.. Keeps the oil in the rocker arm area from cooking.
The rams horn manifolds are very prone to coming loose if you use poor quality bolts.
If you can find a set of rams horns for a '55-57 T-Bird with dual exhaust you can eliminate the front cross over pipe on your Y-block. The left had manifold will have a rear drop in lieu of the front. I have the part number for the Bird manifolds.