Original 40 Series, or Delta Flows?

['70 C/10 SS500]

I'm going to be doing the exhaust on my Caddy 500 powered truck probably next weekend. I ordered original 2 chamber Flowmaster 40 series 3" center in, center out mufflers a week ago but when I got them, they turned out to be all the above, EXCEPT that they are the Delta Flow mufflers instead. They said they can't get non-Delta Flows anymore, so shipped the D.F.'s instead. My question is: Does anyone have first hand experience with the difference between original 40 series and Delta Flow 40 series? I want the loudest exhaust but if there is only a marginal difference between the two, then I may forego the hassle of shipping them back and just use D.F.'s. It will NEVER be too laud for me. Sound QUALITY is a measurable and tangible thing to me, but it can NEVER get too laud! My idea of "IDEAL" exhaust note is the bad-ass sound of my uncles sand rail running a 14:1 230cid alum. block Buick V-8 motor with open headers at about 6000 rpm! (and everywhere in between actually!!) That READS like a small motor, but if you didn't know better, just going off the sound of it you'd think it was a full race big block!

Ok, sorry for the tangential detour.....My combo is: '70 C/10 SWB Caddy 500cid/TH-400 with stock manifolds going into dual 3" pipes into mufflers directly under the cab floor boards OUTSIDE the frame rails exiting with tips centered right at the back edge of the door.