I am running a 78 440 in my pickup. Right now it has 516 heads on it, a cam of unknown origin,( perhaps it's an rv cam) and it runs fine. I am about to pull the engine to replace some seals and swap in a fresh Summit #6400 cam that is 214/224 duration at .050, with a lift of .445/.466. Basically a factory style Magnum cam. I've heard that I would be better off using an open chamber 452 head, rather than using the 516. The engine is a low mileage motor home mill with the low comp pistons. I would appreciate constructive thoughts on this. Thanks.

You need the closed chamber heads NOT the open, if you are wanting to change heads I would get some Stealth heads, they flow better than what you have & have closed chamber, cant rebuild a set of stock iron heads for what the Stealths cost

I agree, you need the closed chambered heads. If you want to make them a little better put 1.74" exhaust valves in them, they already have the 2.08" intakes.

If the valve guides and seats are still good in your 516s Id have a valve job done or at least hand lap the valves and seats. New springs and call it a day. If the guides and seats need replacing then your getting into some $$$. If your good with a die grinder you could smooth out casting irregularities in the int and exh ports. Not a Hog job mind you just removing rough as cast finish and sharp edges.

Edlebrock makes a RPM head that has 75.0 CC chambers built to compete with the 440 Source head prices, I think Summit has them listed at $750.00 each
2.14 intake valves with 1.81 exhaust and they flow a bunch better than any stock Mopar head including the stock M.W. heads

I agree with everything that has been stated. So, you need to decide what is your budget.

Depending on your combined budget and goal. Yourpriority might be somenthing like this going from less expensive/lower performance to larger budget with higher performance.

1) Freshen-up your current 516 heads.
2) If your heads are alread good (unlikely) then just have them freshened-up and maybe a bit of work (larger valve and bowl work)
3) Get some Stealth heads
4) Get some 75 cc Eddy heads.

For where you are at, switching to an open chamber factory head verses using what you have will be a wash.

The 516's that are on it now were rebuilt when I put them on 2000 miles ago. New guides, hardened seats and new HP springs. Not sure why bigger exhaust valves were not installed when they were at the shop. Bought them cheap. $200 for a set of fresh heads was a good deal to me. I only ask because I also have 2 sets of 452's that are in excellent condition. I am retired from a machine shop and have checked them out. I can say that I wouldn't hesitate to bolt them on and go. I suppose that since the 516's are already in place, I should leave them alone and just swap the cam when I seal the engine back up. This engine will probably not see 5000 rpm anyway. It's in a 77 D100 short wide box. The last time I made a dump run I ran across the scales on my way out, it weighed 4000lbs with me in it. It scoots along ok and is fun to drive.

Agree, clean them up and install cam then enjoy, not everyone needs a Hellcat 440. A torque cam is your best bet to move that heavy truck around and makes it fun to drive.