Big Block Truck Headers/Exhaust manifolds

Looking at my truck, It looks like the only thing in the way of a rear dump manifold is the oil filter. No filter back there on the 440, so....

IIRC my 318 has a rear pickup and pan. How can you tell which end is the front or rear on a big block oil pan?

j
On trucks, vans, and motorhomes it's easy to tell front or back on a big block pan. The fitting for the dip stick tube is on the drivers side.