Bill...I will have to look back thru my files and see if I can find it....here is the link to the 4 row units. I believe we have the middle one... because the unit does have the tranny cooler connections. Both cars have an OEM fan shroud setup...we have one in our 68 BB car w/TH400 with a modified roller motor...works good...the other is in a basically stock 1970 L78/TH400...again it works fine. I might add that I have a Stewart HI-perf water pump on the 68...matching thermostat..aux. trans. cooler..and 6 blade steel fan...stock shroud...the 70 has stock water pump, hi-perf stat, flex fan, stock shroud, aux. cooler...
***BB cars generate a lot of heat (as you know)...I don't drive them in 90* weather//with headers it just gets too warm.
That optima unit sounds interesting...since you have a 4 speed it might be the best route to go..not sure about the shroud.
hope this helps...tew
http://www.usradiator.com/chevrolet-...-9991.html#OPT