is it necessary to run 1 5/8" headers with stock heads?

The reason i ask is the other day i was using my temp gun and found that from the front cyl to the rear cyl was about a 60-80 deg f difference.

I then started to think about getting headers, just shorties so then i could always put them on my 4x4 if i decided to upgrade later. The only shorties i found with a 1 5/8" where jba's and i was quoted around a $1000 cdn . With that in mind I found other cheaper brands but they only have an 1 1/2" tubes. I also found a set of longtubes with 1 3/4 tubes/ 3" collector but i'm sure that would be over kill and would require other exhuast work.

So I guess what I'm sayin is 1 would the shorties even the heat distribution out of the heads exhuast port? 2nd if the exhuast ports are only 34 mm (1 5/16") does it really matter if 1 1/2" were used instead of 1 5/8?

BTW i know it may not increase power much or at all but one would think an even temp out of each cyl would be a good thing.

 

so is it a good idea to get the ceramic coating or just the painted headers?