You can put the regulator in the back but it doesn't then compensate for any pressure drop across the lines/fittings or filter.

If you have a big enough feed line, not many 90deg fittings and the filter before the regulator it doesn't matter as much.

IMO it's best to have it near the engine. Easy is feed one rail, crossover in front and return from the other rail into the regulator. (I don't like flowing through a regulator on the feed side but I know some do this).

On my car I did basically as turbobitt described.

Feed line under the intake to a Y, to both rails. Back of rails into the regulator.