292 power steering head bolt/stud

[Seanext]

I am putting together all the parts to install power steering on my K10 with a 292. I have the main bracket however it must be from a larger truck or a school bus because I have never seen one like this before, it is built very strong and is made of cast iron. The top two bolts go over studs that are on the front two head bolts, and the bottom one goes under the water pump bolt. The part number in the parts book for the head bolt is 383490 which is replaced with 9787075. The dimension listed are 1/2-13 3/8-16x4.8. Does anyone know of a source for these studs. I have the engine rebuilt and about to install the head and would like to find the studs before I torque every thing down.