With 5 bolts (the SDs have 8 or more if I'm seeing them correctly) it is an FT. The intake manifold should extend under the valve covers. If so, FT for sure. I take it you know the FE motor, here is a pic of the SD motor:
330, 361 and 391 were the sizes. The 330 was a small bore (3.8something, I can't recall) with a 3.50 stroke. 361 was same as a 360, 4.05 x 3.50 and the 391 was the same as a 390--4.05 x 3.78. The 361 and 391 were also designated 359 or 389 late in their runs. These were detuned (even more detuned) smog motors.
Why Ford would designate different CID's for the same bore and stroke motors (also done with the 352 FE, a 4 x 3.50 vs. the 351C, W & M, all 4 x 3.50 motors) is anyone's guess. As a famous motorist in LA said once, "Beats me!!!!"
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