I took the oil filter/cooler t-stat housing apart to take a look and actually you can tee into the oil cooler return line, it dumps right into the oil filter. The t-stat only acts on the cooler input line. This setup would benefit from a check valve when the t-stat is open to prevent any backflow. BUT what i ended up doing was to drill out the end of the housing attachment bolt (to .5625) & welded a -10 fitting to it. The center bore of the bolt feeds right into the engine and bypasses the filter, no flow restrictions and the filter will function as a check valve due to the pressure drop resisting any backflow ....problem solved.

Thanks for all the input.

As a side note, the block plug that resides just rearward of the filter is a handy way to drain all the COOLANT when the season is over.

Regards, chris