Car is going to be a semi daily driver as weather permits. My goal for the car is strictly a cruiser ( looking at getting a 1973 duster ). Gas mileage isn't a huge concern but yet I'm for better than 5mpg. Rear gearing, I thought about either a 3.23 or a 3.55 gear ratio. I don't want the engine spinning at 3,500 rpm's at 70 mph. If I need to change the torque converter that's okay. Are mopar small blocks known for coil bind with cams over a 0.515" lift?
Yes. Possibly before. Among a grocery list of other things, you need to have the machine shop check retainer to guide clearance and machine guides as needed.
I thought about running the pistons at zero deck height, with a head gasket that has a 0.039" compressed thickness and 1.880" intake valve's, will I have piston to valve clearance issues?
Probably not, but again, remember the grocery list of things to check? This is on the list.
Do I need to run closed chamber heads?
No.
I'm wanting to select the right parts so that my combination will work well. Also, if I was to buy bare cylinder heads are the seats already cut for a certain size valve?
Yes, unless the heads are unfinished. 99% of what you see in Summit, Jegs, etc., are finished with guides and seats installed.
Since my goal isn't 400+ horsepower I was thinking of using 1.880" intake valve's and 1.600" exhaust valve's with a comp valve job and back cutting the valve's, bowl clean up. Am I going in the right direction or am I totally wrong?
No, it looks like you're asking smart questions trying to formulate a game plan. There are lots of really smart people on this site. Glean from them and you'll be ok.