Someone ground the L20B off and re stamped it but that looks like an L20B block. L16/18s have the block vent pipe come straight out to the side behind the exhaust manifold while the L20b points upward. something to check. Also the L20Bs that I've seen did not have that oil filter boss with the four bolt holes around the outer edge. It's remotely possible that that is a Z22 block. There is a blank boss on the same side as the L series that could have been stamped. The Z22 boss is between cylinders 2 and 3 but now under the intake and exhaust. It might still be there but very hard to get at.
Over on the right on the other side you can just make out the unused boss where the L stamp would be... Also note the block vent hole is vertical.
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That looks like a Stanza gearbox to me. Is the reverse up near where 1st usually is??
It's an FS5W71B L series 5 speed made after '80. (has a reverse check sleeve and the retaining bolt and key for the speedometer pinion is not visible so must be in the 6 o'clock position... another indicator of an '80s transmission. This is not a dogleg box.
Ok any benefits to having the L20 head over the 1600??
On an L16 no benefit as any L head other than the 210 will lower the compression. An open chamber L head will drop an L 16s compression to 6.72 and larger valves won't make up for that. Even a closed chamber head like the 219 or the V912 drops it to 8.21.