If he checks obviously you have to bet to build a pot. Whatever he would call with a high spade would seem perfect, if that is half pot bet that, if you think he'd call more try to squeeze some extra but I would go for $25 or so. Your only chance to get him all-in for him to catch something and bet the river, if he does that it's an easy push of course.
You bet $25 on the turn and he calls, pot is $90 on the river and he has $75 left. Any bet from him will mean he's committed and if you push after he checks it won't be an overbet. Just hope for an Ace or spade (but not the
) to come on the river.
If he bets the turn it seems like it will be an easy stacking (unless he has 22..). If it is $20 or more you could just do a miniraise and he will pretty much be committed.