Thank you for your answer kennyd!

I am refering to a standard 1992 model Chevrolet small block 5,7L. (not a LT1)

The car will not be equipped with AC or power steering.
The waterpump who followed the motor is therefore a long type pump.

I have an electric fan whitch is intended to be placed at the rear of the radiator (more efficient than front mounting anyway). It is rather slim. It will be needing app 3 inches of space behind the radiator
I'm planning (but have not quite decided) to rebuild the waterpump to electric powered function to save some power to the rear wheels.

Because I've moved the firewall app 3 3/4 inches further rear, I will be able to move the engine one or maybe 2 inches further back than the recommended postition (the HEI distributor I bought is huge!)
It is a steel body.

But from what you tell, I'll probably needs a short waterpump anyway.

Once again thank you for your answer!