Ed:
<font color=blue>is the unit 59 inchs to the outside of the tires? with 26x12x12 - and 116 inches long front tires to back of frame </font color=blue>
YES
<font color=blue>could a different profile / offset wheel fit to make the unit 2-4 inchs narrower or would it interfere with the disc brakes </font color=blue>
You'd have to go with a narrower tire or a much taller rim. There is next to no clearance between the inner sidewalls and the brakes.
<font color=blue>is the muffler integrated - any way to take a pipe out the side - bottom rear and up - could use a better muffler to quiet it down </font color=blue>
I stared at that a lot and bought a pair of Pro Ears. It isn't integral, but space is limited. It blows out through the expanded metal cover. Any change would involve cutting a hole somewhere else and some tight plumbing, close to other things.
<font color=blue>do you think that the grass clogs are reason for the overheating problem in heavy mowing or does it need extra cooling capacity - is that possible?</font color=blue>
Grass/chaff clogs are the only problem. In 95 degree weather, it runs a bit hot on the gauge, but stable, even at full chat. There isn't a lot of reserve cooling capacity, but when the cooler itself is clear, it is completely stable. John Coxon and I have had pretty good results with insect screen pre-filters. If Power Trac doesn't devise a fix, next summer I'll have tighter screen all around and a centrifugal filter out back.
Terry Estep at Power Trac found that there is an agricultural model cooler for this model Deutz, but didn't have one in hand when I last talked to him. I don't know how it differs.
<font color=blue>I kind of like the 1430 length at 106 inches</font color=blue>
With my new carryall rack, mine is about four feet longer than that. I didn't hurt anything yet - of course I've only backed it into the shed once on Christmas Day.