Look/SPD-SL?
 

Can the same cleat fit a Look and a SPD-SL pedal??

No

you may have a shoe that can use either, but not both at the same time
there are 3 bolts for Look, and 2 bolts for SPD, on many current roadie bike shoes.

I've tried using spd-sl cleats with an old pair of dura-ace 7400 pedals (look delta) at someone's suggestion and while I was able to clip in/out without issue, the interface was too loose for comfortable riding.

To the OP, No.

SPD-SL uses 3 bolts, not 2. (SPD uses 2, but is not a road cleat system, and most modern road shoes are not outfit to mount an SPD style cleat.)
Most modern road shoes can interchange a Look cleat to an SPD-SL cleat. While you can't use the same cleat interchangeably, you most certainly can use the same shoe to interchange cleats.

Thanks much for the feedback.:beer:

I had just purchased a bike that has LOOK pedals on it. I have SPD-SL pedals on a bike and several shoes/cleats for them. Looks like I will be selling the LOOK pedals..

http://www.cehoward.net/delrayb22.jpg