I should be doing other things... so I went ahead and ported the Konami 053245 (sprite) chip, Konami 053251 (palette/priority) chip, and fixed a K052109 bug.
So Surprise Attack is now up and running.
Btw, in case you were wondering, the 053245 is also used in Lethal Enforcers, Parodius, and some games on the TMNT driver (Lightning Fighters, Bells & Whistles, Golfing Greats, TMNT - Turtles in Time, Quiz Gakumon no Susume, and Sunset Riders). ^^