Today I received a BB34 head and have put it side by side with a BB32 head which I bought and have modified to fit on my Daytona replica. The differences between these two are almost the same as photos you posted. I am certain the 350 head is correct as the combustion chamber is definitely smaller to suit 350 bore.
Differences I see easily are.
1) height, 350 is 95.5mm and 500 is 85.7mm
2) 8 fins on 350, 7 on 500
3) 350 is about 15 degrees downdraught, 500 is is nearer 7 degrees.
4) 350 casting thicker, less defined, sand cast? 500 is neater, thinner fins, better detail etc.
5) 350 exhaust outlet, ø42mm, 500 is ø46mm
6) 350 part number on bottom face, 500 part number on side of inlet valve housing,
7) gap between fins at front of pushrod tube not as deep on 350 (1/2”) and nearer 1” on 500
8) all holding down threads on 350 are ø3/8” x 26tpi, 500 has ø7/16” on the long head to crankcase bolts
9) valves are different but my 350 has non standard valves so cannot compare dimensions
10) 350 head might have cast number 65-1757 & 67-1805, very hard to determine with confidence
11) 350 inlet port ø28mm, 500 is ø29.7