Well, check your check valve fittings.
If your fitting screws directly into the manifold, then you have the early style.
If it has a nut that screws onto a coupling in the manifold, it is the later one, and the cheap and easy setup for that is a pair of these from Lowe's:
They are a 5/8" flare cap, and can be had very cheap.
I'd go ahead and get the ones you ordered regardless if they fit or not, as you can usually sell them on here QUICK if they dont.
2 other indicatos of the later style:
-The passenger side has a hose that goes from the pipe to the check valve in a clumsy circle over the valve cover.
-Fuse 3 in the underhood fuse box is 25 amps as opposed to 20 amps on the older style.
'94 Impala SS
#14 of all TRI-9 Impalas
Kore3 C5 front brakes
WX3 Performance C5 rear brakes
Hotchkis springs/bars/rear LCAs
CIA Quad 1 Cermachromed headers
Muffler Man stainless X-pipe/Dynomax UltraFlo mufflers
Street Trends Smoked Euro Head Lights
RMCR rear with Trutrack and 3.42 gears
"Up front there ought to be a man in black"--Johnny Cash
"Is there anything beer CAN'T do?"-- Hank Hill