4.0 cylinderheads different exhaust port?

[californicated]

Hello first time posting please help all advice is welcome, I have a 96 4.0 ranger, about two weeks ago I had removed my cylinder heads, the reason was I loosing rad fluid and had visible smoke from exhaust ,I could see a visible crack on the passenger side between the valves on the #3 cylinder nothing visible on the drivers side, I take them both down to our local napa for advice on cost of repair well as having them tested well come to find out both of the heads was bad and when they quoted me a price I was in shock I said I would search online for a more affordable set in which I found a pair from a place in Florida I don't wanna say the name of the company yet,I called them up told them the year of my truck bla bla simple easy order bought and paid $410.00 shipped took about a week to get here in California I open them up compare the new ones to my old ones everything looks good until I look at the exhaust port the to new ones are different from my older ones the exhaust on my old set is larger oval shaped and the new set are smaller rounded all the bolt hole all line up my question is will this make a difference in performance, hp., smog please help I would like to get my truck on the road by this coming Monday for I have been without a vehicle for three weeks now I don't wanna put the new ones on if all things don't work out and have to mail them all the way back to Florida. thank you all in advance

 

[Big Jim M]

I don't know about when heads designs were changed. But I do know exhaust port size and shape is critical in developing horsepower. Before installing them spend some time researching the head numbers to see what they were first installed on.
Big Jim

 

[Big Jim M]

I just did a little research and found the round gasket set is from 97 up. I also think I found the 96 to be the only year that head was used. Heads seem to come up to 95 and then start again at 97. So your broke heads seem to be an in between year.
Big Jim

 

[californicated]

I don't know about when heads designs were changed. But I do know exhaust port size and shape is critical in developing horsepower. Before installing them spend some time researching the head numbers to see what they were first installed on.
Big Jim

I looked at my old heads I found a number on the exhaust side of the head 95tm6090ad on the new head new casting not rebuilt I didn't find any numbers in the same location if there was it looks like they was ground off I find this odd, I did find a number on the new heads on the end 215031228355 not sure what this number is my truck has vin x I wonder if I will loose a lot of horsepower with install of the new heads I called the company they said they would work im not sure if I wanna install these heads if im gonna loose a lot of horsepower I do need my truck running by Monday I am starting to think this company I bought the heads from is full of B/S starting with the numbers ground off

 

[adsm08]

Well if you bought a new (aftermarket) casting that number was probably never there to begin with, rather than ground off. The number you did find is probably a serial number.

All of the split that I know of on the 4.0 heads is up to 1994, and 95+ as far as compatibility.