If the WSD +7% On Phorcys really only applies to the first hit, Valkyrie body is going to come out ahead of Phorcys for Upheaval. Also: I only use Upheaval during MS, so ya, AF3+2 shoes.
Using 99 Ukon my base damage per hit during Upheaval is about 292 using this set:
fTP for the WS is going to be 4.58 due to DA.
222*4.58=1337
Using 99 Ukon my base damage per hit during Upheaval is about 298 using this set:
A gain of 6 base damage using Valk instead of Phorcys, (a gain of 8 vit, but lose 5 STR, should mean -1 fSTR but +7 WSC for a gain of 6) and also a gain of 3% TA.
fTP for the WS is going to be 4.7 due to the DA and extra TA.
228*4.7=1400
This amounts to a 4.71% increase in base damage per hit, which should mean a 4.71% damage increase for the WS's overall damage.
If Phorcys 7% WSD only applies to the first hit, and we know all hits for Upheaval have the same fTP(1), this means we can divide 7 by 4 to see that it's a 1.75% damage increase overall for the WS (not counting DA, which would lower this number) The +24 attack from Phorcys body would need to increase WS damage by 2.96% to make Phorcys the better choice, but lets face it, 24 attack cannot make up that difference, and I have already skewed all the numbers into Phorcys favor whenever I could. But hey, feel free to correct me if I'm wrong.