I need a pair of heads for my 350 and a guy i know has a pair of marines heads hes says hell let got for 100 bucks, all they need is new seals. Im wondering is there any difference is cooling for a marine head or will i experience any problems running it on the street?

If the heads are used, and it sounds like they are, have them vatted before you use them. CHeck them on a surface plate and have the magna fluxed for cracks. Lake or ocean water has lots of contaminants and it gets baked on to the water jacket. Boat motors run harder than car engines most are a driect drive, to a degree. They've been using all sorts of fuel too so use caution.

As far as the water passages you'll be fine. They have no EGR and that is basically why the are classified as Marine Motors some refer to them as Off Road engines. You might want to have new stainless steel seats installed just in case.

A good set of Vortec heads complete will run you 500 or less. Jim Pace sells a set that is made to go pre 91 bolt pattern so you don't have to use the vortec intake but the valve covers will still need to be the center bolt type. They are good up to 400 Hp. With some new springs you'll be able to go even higher.

Just a thought.