H engine experts..need your help

This was a 1940 distillate tractor to begin with, but has had the engine replaced at some time.

The head is casting # 6186DD... my older parts book doesn't show it. It does have the 43912D and 43913D kerosene valves in it.

The bore mics at 3.443 + or - .002
The piston skirt mics at 3.431, and the top at 3.414

The block # is the 6397DF

1.This appears to be a 3 7/16 (3.4375") bore to begin with, and has about .068" wear. The ring gap was considerable, but there was very little ridge in the cylinder.

2.The valves were very carboned up. I had done a compression test and got only 55 lbs. 57lbs, when I added oil. The tractor burned oil and fouled plugs quickly and I suspect it was mostly in the valve train.

3. I'm considering getting new pistons and sleeves while I have it apart, but am not sure what to get. With the distillate head, I'd guess it would have lower compression. It currently has flat head pistons in it. Would dome head pistons give much power increase and can they be used in conjunction with the distillate head?

4. The valve length was almost exactly 5" with the exception of one that was about 5.2" long... it did not have the IH part # and must have been replaced at some point. Can the distillate head be reworked for gasoline valves? The parts kits i've seen mostly show 5 5/16" or 5 15/32" long valves. If I replace EVERYTHING,valves, guides, springs etc, is there any reason I could not have the valves listed in the kits? It appears there is no difference in pushrods, or camshaft for gasoline vs Distillate tractors.

any help would be appreciated.... my hair is thinning as it is... I really don't need any more reasons to pull what is remaining out!

3. get new sleeves and domed pistions. I don't think that there is much price difference. A later model or gas head will boost the compression (power) much more than the domed pistons (4-5 X). A higher lift cam (regrind, SH, 300, etc.) makes better use of the increased compression. Don't forget to have the lifters refaced.

4. It looks like IH made the head thicker between the top and the top of the combustion chamber to increase the compression. It would seem that milling the head would be easier, but they did not do that.

So other than that, what is causing you trouble ? I think that one thing to remember is that your motor is 65 years old and has probably worked most of it's life. It made have been repaired in a 'make do' fashion once that tractor was 40 or 50 years old, thinking that it would not last much longer. You will have to decide how you would like it to turn out and fix or replace everything until it is there.