I rebuild a 400 1977 and want to install my alternator but i have nothing but the alternator. What is the simple way to bolt it down ?

 

A long bolt through the alternator and into the bolt hole in the head, but with a spacer between the alternator and the head to get the pulley lined up with the engine's pulleys. Then use a strap from a waterpump bolt to the bottom of the alternator, with a dog-leg in it to line up with the alternator.

I think I can find some pics…

 

Better than just a picture, here's a how-to.