During summer months my coolant temps register 180F unfailingly, except for several mile and greater distances with long 6% grades. Got my diesel reassembled and took a short Interstate run at 70mph. Max temp at 20F ambient temp is 170F. This is fine with me as long as combustion of the fuel is as complete as it is at 180F. Could you folk's advise me as to whether I should partially shield radiator with cardboard, or like material, to bring Interstate temps back to 180F for winter months?

Jamb a big piece of cardboard in there and it wont overheat in Wintertime, the effect of blocking radiator air flow will be minimal. On my diesel Benz I've also jury rigged an air intake pipe from the filter housing to breath heated air off the exhaust manifold. Also you can swap thermostats for one that opens at higher temps. Tstats are generally rated between 68* and 83*

And for anybody interested in replicating the DieselDog heated air intake system here's how it works.....

Get a sized section of aluminium accordion pipe or tubing at plumbling supply or hardware store. Find an old tin can like a tennis ball can, open both ends and make one longitudinal cut. Then cut a circle in the center midsection using diagonal cuts like an "X" and bend the cut flaps upward to accomodate the accordian tubing. You can make other cuts in the can to custom fit whatever exhaust manifold section you attach it to. Mine is wrapped just in front of the header pipe. Then hook it up, thats all you gotta do.