I have a PS unit that came from a 68 elky and am wondering if it will work on a 68 chevelle ss396. The fluid reservoir looks like it bolts onto the radiator support, but most of the pictures I've seen have the reservoir bolted onto the engine block with the pulley. Any input?

The reservior/pump bolts to the block. On my 454 it bolted to the driver side front. There are different steering different brackets for the small block and big block applications.

The 68 & older big block fluid reservoir is remote from the pump and bolts to one of the fender bolts I think.

The early big block cars had a remote reservoir. It was mounted to the front drivers side of the car, right in the corner. One bolt through the top of the core support and one through the drivers side fender. A hose ran from the reservior to the pump which was under the generator/alternator, kinda cool really. Be careful when tightening your P/S belt, don't damage the pump housing with a pry bar. You won't like the price of a new pump.
Grover

You learn something new everyday.
Would a 396 have the bolt holes to attach it to the block. And then you could use the newer style pump/res?

Monteman,
Not sure but I don't think it would fit, at least on mine. It would be nice since the price of a combined unit is $56.00 and the remote is $150.00, for a repop or rebuilt. Rebuilts are scarce.
Grover.