I have a 1966 Chevy C20 Custom Camper with a mild-build 327, double-hump heads, a cam and center-dump Ram's Horn exhaust manifolds. It has 2-1/2" aluminized pipe, Series 40 Flowmasters and exits out the rear. It is pretty loud, especially at highway speeds. I think this one would be too loud, if it exited anywhere else, but the rear.
Out the back with stainless steel, angled tipsI have a 1966 Chevy C10 lwb fleetside with a stock 327, a 2-barrel and ceramic-coated FlowTech headers. It has 2-1/2" aluminized pipe, Series 40 Flowmasters and exits out the rear. It is pretty mellow, even at highway speeds. I think this one could exit out the rear or anywhere, in between, and not be a problem.
Out the back with stainless steel, angled tips I think the trend is out the back, but I think it is purely a matter of personal preference. I like the looks of tips exiting the rear, as well as, just behind the rear tire. The '66 K10 I just finished, turned down just over the rear axle.
FlowMasters turned-down, just past the rear axle Turned-down to make room for the spare tire 
