@Derick2k looking through some of the rom board pictures you sent me and compairing the custom chips to what's documented in MAME is pretty interesting:
Desert War
Custom chip: SS91022-10 9513EV 367821 06441
*full chip number isn't documented in MAME but yours isn't on a sub-pcb
Gratia
Custom chip: SS91022-10 9513EV 370121 06441
*this might be gratia set 2, but the full chip number isn't documented in mame, however this appears to be the same chip as tetris plus 2
Idol Janshi Suchie Pai II
Custom chip: SS02-48-01 9410EV 436091 06441
*Idol Janshi's custom chip isn't documented in MAME but this chip seems to be the same as P47-Aces
Angel Kiss
Custom chip: SS92047-01 9423EV 450891 06441
*full chip number for Angel Kiss isn't documented in MAME but this chip appears to be the same chip as Gradia Set 1
Best Bout Boxing
Custom chip: SS92046-01 9338EV 436091 06441 (this chip is on a sub PCB)
*BBB's custom chip isn't documented in MAME but this appears to be the same custom chip as Hayaoshi Quiz Nettou Namahousou and World PK Soccer
I'd be curious if that Idol Janshi Suchie Pai could be converted to P47 Aces with a straight rom swap, or that Angel Kiss could be converted to Gradia Set 1 with a straight rom swap as well.
I'm waiting on delivery of 3 mahjong carts, I'm anxious to see if they share customs with any of the shmups.