Villain is a 40/10 donkey. What type of hand do you put him on? How much do you bet the turn to maximize your expected profit?

Texas Hold'em $20-$40 NL (real money), hand #1,408,858,694
Table El Cajon, 24 Dec 2006 11:25 PM ET

Seat 1: dasstryne ($4,225.00 in chips)
Seat 3: T.Man17 ($1,493.00 in chips)
Seat 5: 1best1 ($1,733.70 in chips)
Seat 6: evilbutt ($2,206.50 in chips)
Seat 7: lesaint_1 ($4,838.45 in chips)
Seat 8: Hero [ :Jd: , ] ($1,730.00 in chips)
Seat 9: ritoznojc ($4,721.00 in chips)
Seat 10: ladoga ($319.45 in chips)
ANTES/BLINDS
dasstryne posts blind ($10), T.Man17 posts blind ($20).

PRE-FLOP
1best1 calls $20, evilbutt folds, lesaint_1 folds, Hero bets $100, ritoznojc folds, ladoga folds, dasstryne folds, T.Man17 folds, 1best1 calls $80.

FLOP [board cards ,:Kd:, ]
1best1 checks, Hero bets $140, 1best1 bets $400, Hero calls $260.

POT $1000
TURN [board cards ,:Kd:,, ]
1best1 checks, Hero bets ?