SBC Exhaust Manifold Bolts

I have a 1981 Chevy 305.
I am installing a set of Rams Horns on it.
However, all the mounting bolts were lost.
I was told that these bolts are 3/8 x 16.
8 of these bolts are one length and 4 of them are longer.

Does anyone know what length each of these bolts are?

Also, 1 of the bolts/studs that holds on the exhaust pipe is missing.

What is the size of this bolt?

And there are 4 small plugs with square heads on each manifold--

What are these plugs called?

I was told that these plugs are 1/4" NPT---is this correct?

If anyone has any of these bolts, I would like to buy them.

Contact: Mike--407-953-5007---drumdoctor at live dot com.

This one example SBC Exhaust Manifold Bolts "RAM Horns" Stainless Small Block Chevy 283 327 350 | eBay
You can also check at Jegs.com, Sumitt Racing Northern Auto,etc.......