10/20 FR : AA and I have position

I get AA UTG and make it 70 to go.
1 caller in MP
SB (solid player with TAGish stats, rarely gets out of line) calls

(~250) Flop is
3 4 5 rainbow

SB leads 1/2 pot (~150)
I call (???)
MP folds

(~750)Turn
3 offsuit
SB leads 2/3 pot (~500)
I ...???

What do you think of my call on flop? I probably should have raised come to think of it but I wanted to see what he would do on the turn if I smoothcall because that is one hell of a dry board. Is this an easy turn muck? He isn't overly aggressive and I read him for a strong hand here. Maybe he's got a smaller PP but a set and flopped straight (67, mayyyyyybe A2s) are also likely.

What's the plan?