[vettestr]

You have been methodical and seem to have a firm grasp on how everything is built or needs to function. I went back to the beginning to re-read all that has been done. Many good suggestions have been added by the gang but you are in the same place so back to basics.

Ron Davis is local for me and taught me a few tricks or system checks. All coolant systems works best under pressure and a magic number seems to be 12.5 PSI as the MIN. and that is easy to verify (a fuel pressure gauge works great). As a tool only install a gauge in the manifold somewhere as a system check. Use water and additives to lube as well as an anti-corrosion agent as I don't agree with the 100% coolant suggestion but water for test period will work fine. You tested T-stat and all flow related items but pressure will be a sanity check. This leaves the engine and it runs well with good looking plugs but a lack of timing would not show up under tests you mentioned. You mentioned No Pinging etc... I know you verified timing against the marks but go 1 step more. I would be tempted to roll in initial timing until it rattled or bumped against starter then check to see what timing marks are showing again as a sanity check. If you have 45* you know the marks are wrong somehow, you could do a piston TDC stop and check marks that way too???? Your A/F ratio looks good and engine runs good but if timing marks are off by 20+ degrees retarded you may not know it on a new install and that would be easy to miss.

The waterpump and pulleys were covered, I use 15% overdriven as the minimum and 20% is even better for pulley ratio. You can look for more issues with fans and all that but if it overheats at hi-way airflow with shrouding on the inlet side and any fan working on puller side I would suspect engine caused issue. How about some new photos of rad inlet/outlet sides with shrouding?