observed hand: crazy flop action with bottom set on dry board

[creedofhubris]

$5/10 NL. $1000 stacks.

8 people in a limped pot. Hero has 33 in the BB and checks. Hero is known as a TAG who likes to trap on occasion and who is not a bluffer.

Flop:

J[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/spade.gif[/img]

Very solid SB, who has logged a lot of hands with hero and who is a big winner overall in this game, bets $40.

Hero calls; SB is capable of making big laydowns and a raise might give things away.

Solid TAG makes it $120 from MP+1.

An unknown in CO makes it $350.

Folded to the SB, who calls the $350.

Hero's action?