I'm not a 727 expert, but I cant think of one part that is not interchangeable. I lifted this off of another web site if you want to verify big or small block:

It's EASY to tell them apart if they're not attached to an engine. Course, I take for granted you can tell a 727 apart from a 904 from the pan. However, big and small block 727s are simple to distunguish. The small block version only has two torque converter dust cover retaining bolt holes across the bottom of the bell housing. The big block version has four. Of course, the bolt patterns are different, but the dust cover bolt holes are an easy fast way to tell.
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