Party 10/20 failed bluff, facing a blockbet on river

Villain in SB is 25/3 over only 70 or so hands with 2500 behind.

UTG+2 makes it 80. Hero calls with A[img]/images/graemlins/heart.gif[/img]k[img]/images/graemlins/club.gif[/img]. Folded to SB who calls.

Flop (250) T[img]/images/graemlins/heart.gif[/img]4[img]/images/graemlins/club.gif[/img]2[img]/images/graemlins/heart.gif[/img]

UTG+2 bets 200. Hero calls. Villain calls.

Turn (850) T[img]/images/graemlins/club.gif[/img]

Check, check. Hero bets 400. SB calls 400

River (1650) 4[img]/images/graemlins/diamond.gif[/img]

SB bets 375, Hero? Give it up because Villain can put me on a four-flush?